Geomorphology, Quaternary Stratigraphy, and Geoarcheology of Fox Creek Valley, Tallgrass Prairie National Preserve, Northeast Kansas
Rolfe D. Mandel
Kansas Geological Survey 2006
GEOMORPHOLOGY, QUATERNARY STRATIGRAPHY, AND GEOARCHEOLOGY OF FOX CREEK VALLEY, Tallgrass Prairie National Preserve, NORTHEASTERN KANSAS
Rolfe D. Mandel Kansas Geological Survey University of Kansas
2006 Kansas Geological Survey Open-File Report 2006-29
Prepared for National Park Service
Acknowledgments
This investigation was funded by a grant (Award No. H6067A00009) awarded by the National Park Service. Support also was provided by the University of Kansas’ Odyssey Archaeological Research Fund. Dr. Darren Gröcke, Director of the Stable-Isotope Biogeochemistry Laboratory at McMaster University, assisted with δ13C analyses. Thanks also go to Dr. Arthur Bettis and Adel Haj at the University of Iowa’s Paul H. Nelson Stable Isotope Laboratory for assisting with δ13C analyses. I am grateful to a number of individuals at the Kansas Geological Survey who assisted with the production of this report. Jennifer Sims, Pat Acker, and Nick Callaghan prepared the illustrations, and John Charlton prepared many of the photographs. ShyAnne Mailen assisted with copy editing, Bob Sawin and Rex Buchanan reviewed the manuscript, and Jennifer Sims formatted the volume. Also, I am grateful to Jared Beeton, Ph.D. candidate at the University of Kansas, for helping me in the field. Finally, the following staff of the National Park Service provided assistance: Steve Miller, Paula Anderson (now with The Nature Conservancy), Bruce Jones, Ken Cannon, and Kristen Hase. Thanks to all of them.
ii ABSTRACT
A geomorphological investigation was conducted in Fox Creek valley within the Tallgrass Prairie National Preserve, Chase County, Kansas. During the first stage of the study, Quaternary landforms were defined and mapped in the valley. This was followed by inspection of cutbank exposures along the creek and deep coring across the valley floor. Subsurface information gleaned from the exposures and cores was used to determine the lithostratigraphy and soil-stratigraphy of the landform sediment assemblages. The numerical ages of alluvial deposits and associated buried soils were determined by radiocarbon dating charcoal, plant macrofossils, and soil carbon. The radiocarbon chronology, combined with soil-stratigraphic data, was used to define temporal and spatial patterns of landscape evolution (erosion, deposition, and landscape stability), and to assess the geologic potential for buried prehistoric cultural resources in Fox Creek valley. Also, late-Quaternary vegetative change was inferred from δ13C analysis of soil and sediment organic carbon. The valley floor of Fox Creek consists of four Quaternary landforms: a low floodplain -0b),(T a slightly higher floodplain (T-0a), an alluvial terrace (T-1), and alluvial/colluvial fans. Members of the DeForest Formation, a lithostratigraphic unit that occurs throughout the eastern Plains, compose all of the Holocene landform sediment assemblages (T-0a, T-0b, and T-1) in the valley. Specifically, the T-0b surface is underlain by stratified, silty and loamy alluvium typical of the Camp Creek Member of the DeForest Formation. Although the numerical age of the T-0b fill is unknown, it probably is less than 400 years old and may be less than 200 years old in most of the valley. Two units of the DeForest Formation were identified beneath the T-0a surface: the Honey Creek Member and the Roberts Creek Member. The Honey Creek Member consists of brown (10YR 5/3-4/3, dry), silty alluvium with a moderately expressed surface soil (A-Bw-Bk horizonation). The numerical age of the Honey Creek Member in Fox Creek valley is unknown, but it aggraded sometime after ca. 2000 14C yr B.P. Aggradation of the Honey Creek Member was interrupted by at least one episode of landscape stability, indicated by a weakly developed soil about 1.5 m below the T-0a surface. The Roberts Creek Member consists of fine-grained, organic-rich alluvium that fills paleochannels cut into the Honey Creek Member. A subtle 1 m-high scarp separates the T-0a and T-1 surfaces in Fox Creek valley. The T-1 terrace dominates the valley floor and gently rises towards the valley wall where it either merges with alluvial/ colluvial fans, or is bounded by a steep bedrock wall. The Gunder Member of the DeForest Formation forms most of the valley fill beneath the T-1 surface. It consists of moderately oxidized, brown (10YR 5/3, dry) to yellowish brown (10YR 5/4, dry) silty clay loam that has been strongly modified by surface-soil development (A-Bt-Btk horizonation). Aggradation of the T-1 fill was underway at ca. 11,200 14C yr B.P. and may have continued into the early Holocene. However, there is a gap in the alluvial record between ca. 11,200 and 4500 14C yr B.P. The early-through-middle Holocene appears to have been a period of net sediment removal on the valley floor of Fox Creek. Sediment storage resumed during the late Holocene and was characterized by rapid floodplain sedimentation from ca. 4500 14C yr B.P. until sometime between ca. 3500 and 2100 14C yr B.P. By ca. 2100 14C yr B.P., sedimentation slowed, and soil development was underway on the late Holocene floodplain soon after 2100 14C yr B.P. There was another episode of floodplain sedimentation sometime after 21001 4C yr B.P., resulting in burial of the soil only on the lowest portion of the T-1 terrace near the stream channel. Large, low-angle alluvial/colluvial fans on the margins of the valley floor are composed of fine- and coarse-grained sediment that accumulated during the late Pleistocene.The top of a strongly expressed, brown (7.5YR 4/3, dry) to reddish brown (5YR 4/3, dry) buried soil (paleosol) with At-Bt horizonation is about 1.25-1.50 m below the surface of the fans. Decalcified organic carbon from the upper 10 cm of this paleosol yielded radiocarbon ages of 24,560+350 and 22,620+340 yr B.P. Based on the lithology of the alluvial/colluvial deposits, the fans are composed of the Severance formation, an informal lithostratigraphic unit recognized in eastern Kansas and Nebraska. The δ13C values determined on organic carbon in soil and sediment samples from Core 3 (T-1 fill) suggest that between ca. 4500 and 2100 14C yr B.P., the valley floor of Fox Creek was characterized 13 by a mixed C3/C4 plant community. However, there is a distinct shift to less negative δ C values after 14 ca. 2100 C yr B.P., suggesting that C4 vegetation (i.e., warm-season grasses) increased in abundance
iii at the expense of C3 plants (i.e., trees). The increase in C4 vegetation may represent warmer (and possibly drier) conditions and/or increased fire frequency, which would have reduced woody plant cover in the valley. Results of the geomorphological investigation indicate there is high potential for buried Late Archaic and Early Ceramic cultural deposits in Fox Creek valley. These deposits will be associated with the T-1 fill (Gunder Member), as was observed at site 14SC1304. In addition, the T-1 fill may harbor Early Paleoindian cultural deposits, although this potential is only moderate because no buried soils were observed in late-Wisconsinan alluvium beneath the Gunder Member. Also, there is high to moderate potential for buried Early through Late Ceramic cultural deposits in the T-0a fill, and Historic cultural deposits may be buried in the T-0b fill.
iv INTRODUCTION
The Nature Conservancy and the National Park Service cultural resources. Hence, this investigation was conducted to have plans to restore vegetation and natural surface runoff provide baseline geomorphological and geoarcheolgical data for along Fox Creek, the primary drainage in the Tallgrass Prairie the area of Fox Creek valley within the Preserve. National Preserve. Specifically, the lower reach of Fox Creek at The primary objectives of this investigation were to (1) the southern edge of the Preserve will see the reestablishment of define and map Quaternary landforms and lithostratigraphic units plants that reflect the natural pre-Euro-American contact tallgrass in Fox Creek valley, (2) determine the soil-stratigraphy of the prairie ecosystem. A short distance upstream along Fox Creek, landform sediment assemblages, (3) determine the radiocarbon row crops will be planted that reflect the cultural landscape at ca. ages of alluvial deposits and associated buried soils in order 1880 when rancher Stephen Jones owned and operated the Spring to define temporal and spatial patterns of landscape evolution Hill Ranch. The commitment of these two locales to long-term (erosion, deposition, and landscape stability) in the valley, (4) use for either tallgrass prairie or row crops will make subsequent reconstruct late-Quaternary vegetative change in the study area identification, dating, and interpretation of landforms and late based on δ13C analysis of soil and sediment organic carbon, and Quaternary deposits along Fox Creek more difficult. Also, future (5) assess the geologic potential for buried prehistoric cultural projects that involve land modification, including the removal of resources in Fox Creek valley. agricultural terraces to restore natural drainage, may affect buried
ENVIRONMENTAL SETTING
Physiography and Bedrock Geology streams in the region have steep gradients and deeply entrenched channels bordered by rocky ledges. From an archeological perspective, the abundance of The Tallgrass Priarie National Preserve is in the Flint Hills chert bands in the limestones is perhaps the most important region of Fenneman’s (1931) Central Lowlands physiographic characteristic of the Flint Hills environment (Mandel, 2006a). province. The Flint Hills trend north-south along the western Because of its superior flaking qualities, Flint Hills chert edge of the Osage Cuestas and Glaciated Region of eastern provided excellent raw material for chipped stone tools and was Kansas. The Flint Hills region derives it name from the heavily exploited by prehistoric inhabitants of the region. abundance of chert, or flint, scattered across its surface. Like the Osage Cuestas to the east, the Flint Hills were formed by erosion of westward-dipping strata. The rock units are Permian Quaternary Geology in age, and limestone members in the region contain many bands Pleistocene Stratigraphy of chert. Because chert is much less soluble than the limestone that encloses it, weathering of the softer rock forms a clay-rich The Pleistocene stratigraphy of the unglaciated portion of soil that contains a large volume of chert fragments (Wilson, the Flint Hills region is based on a framework of late-Quaternary 1984:19). This gravel-rich soil armors the rocky uplands and loesses, alluvium, and colluvium. Although loess has not been causes slower erosion than in adjacent areas where the limestone documented in the Tallgrass Prairie National Preserve, these does not contain chert. deposits are regional in extent and thus provide references Surface features and the geologic structure of the Flint Hills to which more localized fluvial and colluvial units can be region are similar to those in the adjacent Osage Cuestas, but stratigraphically related. Therefore, recognition of the loess a prominent rocky escarpment nearly 100 m high separates the stratigraphy of northeastern Kansas is relevant to this study. regions. This escarpment, which forms the eastern border of the At least four stratigraphically superposed loesses occur in Flint Hills region, is the most rugged surface feature in Kansas northeastern Kansas: the Loveland, Gilman Canyon, Peoria, and (Self, 1978:44). The east-facing slope of the escarpment is Bignell (Mandel and Bettis, 2003a). The Loveland loess is the composed of resistant cherty limestones interbedded with softer most widespread pre-Wisconsinan loess in the Midcontinent. It shale layers. Weathering of the shales has created a landscape that is typically yellowish-brown or reddish-brown eolian silt that resembles step-like benches. The highest of these benches form reddens (as a result of weathering) toward the top of the unit. the uplands of the Flint Hills. The uplands are gently rolling, Regional stratigraphic relationships suggest that the Loveland especially towards the western boundary of the Flint Hills. loess in northeastern Kansas is Illinoian in age (Marine Isotope Major rivers and streams have dissected portions of the uplands, Stage 6), and that the Sangamon Soil developed in the upper part forming prominent strath terraces. These terraces are erosional of the unit is buried by Wisconsinan deposits (Follmer, 1978). surfaces cut across bedrock as stream channels laterally migrated Luminescence dating (TL and IRSL) at the Loveland paratype and downcut, leaving little to no alluvium on the rock-cut straths section in western Iowa and the Eustis section in south-central (Mandel, 2006a). Many of the small, first- and second-order Nebraska indicates that the Loveland loess was deposited between about 160,000 and 130,000 yr B.P. (Forman et al., 1992; and alluvium, and (3) the numerical age of the colluvium and Maat and Johnson, 1996; Forman and Pierson, 2002) alluvium. Subsequently, Mandel and Bettis (2001a) established The upper part of the Loveland loess is weathered to the the Severance formation, an informal lithostratigraphic unit Sangamon Geosol. This pedostratigraphic unit is usually well consisting of colluvium and alluvium underlying in situ or expressed and its color ranges from a vivid to pale reddish- reworked Peoria Loess on slopes and alluvial terraces in the brown. Constraining TL and radiocarbon ages indicate that the Central Lowlands. The type locality for the Severance Formation period of pedogenesis could have extended from about 125,000 is in the Wolf River valley immediately west of the community to 55,000 yr B.P. (isotope stages 5d to 3). At some localities, the of Severance in Doniphan County, northeastern Kansas (Mandel Sangamon Soil represents several soils welded together to form a and Bettis, 2003b). The upper 3-4 m of the Severance formation “pedocomplex” that may represent formation over a longer time are oxidized and often have two or more paleosols forming a span (Schultz and Tanner, 1957; Fredlund et al., 1985; Morrison, pedocomplex developed in them. Radiocarbon ages determined 1987). on organic carbon from the paleosols range from ca. 25,000 The Gilman Canyon Formation is the earliest Wisconsinan to 15,000 yr B.P., with most clustering between ca. 24,000 to loess in northeastern Kansas and was first described in south- 18,000 yr B.P. (Mandel and Bettis, 2003b). The paleosols have central Nebraska (Reed and Dreeszen, 1965). The Gilman thick, well-expressed Bt horizons with brown, strong brown, Canyon Formation is a dark, noncalcareous silt loam that has yellowish brown, and/or reddish brown matrix colors; prismatic been modified by pedogenesis. In northeastern Kansas, the to subangular-blocky structure; iron and manganese oxide stains Gilman Canyon Formation is usually thin (<2 m) and the soil and concretions; discontinuous clay films and silt patches; and developed into it is welded to the Sangamon Geosol. Radiocarbon common macropores. With few exceptions, the radiocarbon and TL ages from the Gilman Canyon Formation range from ages and soil properties are typical of paleosols composing the about 40,000 yr B.P. at its base to 24,000-23,000 yr B.P. at the top pedocomplex of the Gilman Canyon Formation on the adjacent (Johnson et al., 1990; Johnson and Zhaodong, 1993; Mandel and uplands. Bettis, 1995; Pye et al., 1995; Matt and Johnson, 1996; Muhs et al., 1999). Holocene Stratigraphy Peoria Loess, the dominant surficial deposit on uplands and Pleistocene terraces in northeastern Kansas, overlies the Gilman Deposits of fine-grained Holocene alluvium in Fox Creek Canyon and Severance formations, and is typically a calcareous, valley, and elsewhere in the Flint Hills region, strongly resemble massive, light yellowish tan to buff colored silt loam. The those of the DeForest Formation. This formation is a formal thickness of the Peoria Loess is extremely variable, but it tends lithostratigraphic unit originally defined by Daniels et al. to be thickest near major river valleys. Radiocarbon ages from (1963) in western Iowa and subsequently refined by Bettis and the Peoria Loess in the Eastern Plains range from about 24,000- Littke (1987), Bettis (1990, 1995), Bettis et al. (1996), Mandel 23,000 yr B.P. at its base to 12,000 yr B.P. near the top (Martin, and Bettis (2001a), and Dillon and Mandel (in press). The 1993; Johnson et al., 1993; May and Holen, 1993; Mandel and DeForest Formation has been traced into southeastern Nebraska Bettis, 1995, 2001a). (Dillon, 1992; Mandel, 1994a, 1999; Mandel and Bettis, 1995, In some areas of northeastern Kansas, primarily along the 2001a), northwestern Missouri (Fosha and Mandel, 1991), bluffs of the Kansas and Missouri rivers, Bignell Loess mantles and northeastern Kansas (Mandel et al., 1991; Mandel, 1994b, the soil at the top of the Peoria Loess. Where this occurs, the Mandel and Bettis, 2001a, 2003a; Mandel et al., 2006). buried soil developed in Peoria Loess is referred to as the Brady The DeForest Formation consists of eight formal members, Soil (Feng et al., 1994; Schultz and Stout, 1945). Johnson and one of which, the Honey Creek Member, is new (Dillon and Willey (2000) noted that the widespread development of the Mandel, in press). Only four members of the formation, the Camp Brady Soil between ca. 10,500 and 9,000 yr B.P. implies that Creek, Roberts Creek, Honey Creek, and Gunder, have been the loess-mantled uplands were stable during much of the identified in Fox Creek valley. Pleistocene-Holocene transition. Where it is not buried by Bignell The Camp Creek Member encompasses deposits formerly Loess, the soil at the top of the Peoria Loess has either been referred to as “post-settlement alluvium.” This member consists overprinted by modern pedogenesis (Dreeszen, 1970; Thorp et of stratified to massive, calcareous to noncalcareous, very dark al., 1951) or been removed by erosion, along with the overlying gray to brown silt loam to clay loam, though some deposits may Bignell Loess (Johnson and Willey, 2000). Radiocarbon consist of coarser sediment. It is inset into or unconformably and luminescence ages within the Bignell Loess indicate overlies the Gunder, Honey Creek, and Roberts Creek members, that sediment composing the unit accumulated episodically depending on the geomorphic setting and history of land use throughout the Holocene (Mason et al., 2006). (Mandel and Bettis, 2003a). The thickness of the Camp Creek Recent investigations in northeastern Kansas and Member is extremely variable in Fox Creek valley basin, ranging southeastern Nebraska identified colluvial and alluvial facies of from a few centimeters to over 4 m. Surface soils developed in the Gilman Canyon Formation beneath slopes and Pleistocene the Camp Creek Member are Entisols and thin Mollisols with terraces, respectively (Mandel and Bettis, 2001a, 2003a). This organically enriched A horizons grading to stratified, parent interpretation was based on (1) the stratigraphic relationship materials (C horizons). The Camp Creek Member includes of the colluvium and alluvium to the Peoria Loess, (2) the sediment that accumulated after about 400 14C yr B.P. (Mandel morphology and of the paleosol(s) developed in the colluvium and Bettis, 2003a).
The Roberts Creek Member consists of dark-colored, adjacent uplands has been affected by decades of cattle grazing, clayey, silty, and loamy alluvium. This member usually occurs the natural vegetative community is fairly intact. only as channel fills in small (< fourth-order) valleys, but it The tallgrass prairie of the Flint Hills is dominated by forms channel fills and thick flood drapes in larger valleys. In warm season C4 grasses, especially big bluestem (Andropogon the unglaciated area of northeastern Kansas, the Roberts Creek gerardi) and little bluestem (Andropogon scoparius). Other Member can overlie a wide variety of deposits including the common species include switchgrass (Panicum virgatum), Gunder and Corrington members, coarse-grained older alluvium, Indian grass (Sorghastrum scoprius), sideoats grama (Bouteloua and loess (Mandel and Bettis, 2003a). Roberts Creek Member curtipendula), panic grass (Panicum scribnerianum), and June deposits usually occur beneath floodplains and low terraces, and grass (Koeleria pyramidata) (Küchler, 1974). Numerous species it is separated from the younger Camp Creek Member of the of annual and perennial forbs occur in the tallgrass prairie, but formation by either a fluvial erosion surface or a hiatus marked they account for less than five percent of the prairie community by a buried soil. Weakly developed buried soils with A-C or A- (Küchler, 1974). Bw profiles are common in the Roberts Creek Member, but they There is a narrow riparian forest adjacent to the channel of are rarely traceable from one valley to another. In northeastern Fox Creek. This forest is dominated by cottonwood (Populus Kansas, surface soils developed into the Roberts Creek Member deltoides), hackberry (Celtis occidentalis), willow (Salix sp.), elm are thick, black (10YR 2/1, dry) to dark grayish brown (10YR (Ulmus sp.), oak (Quercus sp.), and black walnut (Juglans nigra). 4/2, dry) Mollisols. These soils are morphologically less This ribbon of trees allows woodland fauna, such as whitetail developed and have darker colored B and C horizons than soils deer, to penetrate into the adjacent prairie. Hence, in addition to developed in the older Gunder and Corrington members. The providing botanical food resources, such as hackberry seeds, the Roberts Creek Member ranges in age from ca. 3,000 to 500 14C riparian forest played a role in providing game for prehistoric yr. B.P. (Mandel and Bettis, 2003a). people who occupied the grasslands of the Flint Hills. The Gunder Member consists of strongly to moderately oxidized, dominantly silty and loamy alluvium lacking a loess Climate cover. Lower parts of this member may be reduced and/or coarse grained. In the unglaciated area of northeastern Kansas, Gunder The modern climate of northeastern Kansas is continental; Member deposits occur in valleys of all sizes and unconformably summers are very hot, and winters are very cold. There also overlie coarse-grained and often organic-rich older alluvium, are extremes in precipitation, with years of drought sometimes loess, or bedrock (Mandel and Bettis, 2003a). Younger members followed by periods of excessive annual rainfall. The Flint of the formation are separated from the Gunder Member by Hills region is within Thornthwaite’s (1948) moist subhumid a fluvial erosion surface or a hiatus marked by a buried soil. (C ) climatic zone, where annual precipitation exceeds evapo- Surface soils developed in the Gunder Member are thick 2 transpiration. The C2 climate is characterized by hot, humid Mollisols with brown (10YR 5/3, dry) to yellowish brown (10YR summers and cold, dry winters. 5/4-5/6, dry) Bw, Bt, Bk, and/or Btk horizons. Buried soils occur The mean annual precipitation at Cottonwood Falls, Kansas, within the Gunder Member, but they are not widely traceable or for the period August 1, 1948, to December 31, 2005, is 34.86 useful as regional pedostratigraphic units. The Gunder Member inches (High Plains Regional Climate Center, 2006). The average 14 ranges in age from about 10,500 C yr. B.P. at its base to about maximum and minimum temperature in January is 41.1º F and 14 2,000 C yr B.P. at its surface (Bettis, 1990, 1995; Mandel and 18.6º F, respectively. The average maximum and minimum Bettis, 1992). temperature in July is 91.4º F and 67.9º F, respectively (High The Honey Creek Member is a grayish brown (10YR 5/2, Plains Regional Climate Center, 2006). dry) to brown (10YR 5/3) silt loam that is massive in its upper June and January are normally the wettest and driest months, part and has large-scale trough cross-bedding and epsilon respectively, for the study area. Approximately 75 percent of the cross-stratification near its base. The Honey Creek Member precipitation falls during the six months of the growing season, typically forms a channel fill inset into Gunder Member, but its April through September. This period of high precipitation is stratigraphic position relative to the Roberts Creek Member is largely a result of frontal activity. Maritime polar (mP) and unclear. Surface soils developed in the Honey Creek Member are continental polar (cP) air masses that flow into northeastern Mollisols with A-Bw profiles, and weakly expressed buried soils Kansas during spring and early summer usually converge with with A-C and/or A-Bw profiles are common in this unit. The warm, moist, maritime tropical (mT) air that is flowing north 14 Honey Creek Member aggraded between ca. 3,700 and 500 C yr from the Gulf of Mexico. The overrunning of mP and cP air by B.P. (Dillon, 1992; Dillon and Mandel, in press). warmer mT air often produces intensive rainfall of short duration along the zone of convergence. During late summer, convectional thunderstorms also can produce heavy rainfalls. Vegetation Eastern Kansas is subject to severe drought when the strong westerlies of winter persist into spring and summer. The vegetative cover on the valley floor of Fox Creek is a Intensification of westerly (zonal) airflow in the upper product of recent human intervention. In 1995, most of the valley atmosphere has the effect of blocking the northward penetration floor was seeded with brome grass Bromus( sp.), and the fields of moist Gulf air into the mid-continent (Bryson and Hare, are periodically cut for hay. Although the tallgrass prairie on the 1974:4), thus promoting drought (Mandel, 2006a). Prolonged
severe drought can have significant effects on ecosystems of the carbon. Also, a column of samples from Core 11 was analyzed grasslands. For example, shortgrass prairie in western Kansas for organic carbon content and δ13C values of organic carbon. may respond to drought by expanding eastward into the area of mixed and tallgrass prairie. Also, increased aridity tends to Grain-Size Analysis increase fire frequency in the prairies. The dynamics of drought- related vegetational perturbations and their implications for Soil and sediment samples were air dried and sent to the late Quaternary landscape evolution and prehistoric human University of Iowa’s Quaternary Materials Laboratory, located adaptations are discussed elsewhere (see Mandel, 2006a). within the Geoscience Department, to determine particle-size distribution and organic carbon content. A slightly modified METHODS version of the pipette method, using a known loess standard (Soil Survey Staff, 1996) was used to determine particle-size Field Methods distribution of the samples. Hydrogen peroxide was used to oxidize organic matter in organic-rich samples, and acetic The field investigation initially involved reconnaissance of acid digested carbonate from 10 g samples of the <2 mm Fox Creek valley. At this early stage of the study, landforms sample fraction. The samples were then dispersed in a sodium identified on the 7.5-minute U.S.G.S. topographic map (Strong metaphosphate solution and shaken on a reciprocal shaker City, Kansas, Quadrangle; Figure 1) and 1:5,000-scale black- overnight. Silt and clay aliquots were drawn from the appropriate and-white aerial photographs were field checked, and stream pipette depth based on particle-size settling velocity, oven dried, cutbanks exposing thick sections of valley fill were recorded and and weighed to the nearest milligram. Wet sieving recovered the photographed. Following the reconnaissance, cutbanks deemed sand fraction. The results, presented as weight percentages, total accessible were revisited and described. However, most of the to 100% of the <2 mm fraction. cutbanks were very steep and dangerously high and could not be cleaned with a hand shovel. Hence, nearly all of the soil- Stable Carbon Isotope (δ13C) Analysis and stratigraphic data were gleaned from 6.5-cm-diameter cores Determination of Organic Carbon Content collected with a trailer-mounted Giddings hyrdaulic soil probe (Figure 2). Coring was concentrated at the northern end of the Samples were collected for stable carbon isotope (δ13C) project area in order to sample all valley-floor landform sediment analysis of organic carbon from two cores: Core 3 taken on the assemblages along a single transect (Figure 3). This sampling T-1 terrace, and Core 11 taken on the T-0a floodplain (Figure 3). strategy yielded data needed for preparing a cross-sectional Some of the samples from Core 3 were split and sent to the Paul diagram of late-Quaternary deposits stored in Fox Creek valley H. Nelson Stable Isotope Laboratory at the University of Iowa (Figure 4). and the Stable-Isotope Biogeochemistry Laboratory at McMaster Detailed descriptions of soil profiles were made in the University. This comparative analysis provided quality control. field using standard procedures and terminology outlined Samples from Core 11 also were sent to both laboratories, but by Soil Survey Division Staff (1993) and Birkeland (1999). the Paul H. Nelson Stable Isotope Laboratory closed before Stages of carbonate morphology were defined according to that facility analyzed the samples. Hence, the Stable-Isotope the classification scheme of Birkeland (1999:TA1-5), and Biogeochemistry Laboratory at McMaster University was the sedimentary features preserved in C horizons of some soils were sole source of the δ13C data for Core 11. described to help reconstruct depositional environments. Samples sent to the University of Iowa were received at the Soils were included in the stratigraphic framework of every Quaternary Materials Laboratory, where they were ground to section and core that was described. Soils are important to the ensure homogeneity, then decalcified with 1 N HCl, centrifuged, subdivision of Quaternary sediments, whether the soils are at rinsed three times with ultra pure water to remove excess HCl, the present land surface or buried (Birkeland,1999). After soils and dried. The samples were then transferred to the Paul H. were identified and described, they were numbered consecutively, Nelson Stable Isotope Laboratory where they were weighed, beginning with 1, the modern surface soil, at the top of the wrapped in tin cylinders, and combusted in a Costech CHNS section or core. ECS-4010 element analyzer. Sample weights varied according to depth and organic matter content, as determined by soil Laboratory Methods color using a Munsell® Color Chart. The organic carbon (O.C.) content of the decalcified samples was determined by the Physical and chemical analyses were performed to element analyzer and EAS 3.1 Software. A CONFLO interface characterize and confirm field descriptions of stratigraphic units carried the combusted samples from the elemental analyzer to and soils, assist in interpretation of depositional processes and a Finnigan MAT 252 isotope ratio mass spectrometer, which post-depositional weathering, and reconstruct paleoenvironments. measured δ13C values for each sample. Various National Institute A column of samples from Core 3 was analyzed for particle-size for Standards and Technology (NIST) standards (Acetanilide, distribution, organic carbon content, and δ13C values of organic Sulfanimide, LSVEC-Lithium Carbonate, LIPS, and ANU- Sucrose) were analyzed with the samples to evaluate accuracy. A linear regression analysis correlated the known and experimental standard values; the regression equation then normalized sample
Figure 1. Topographic map of Fox Creek valley (from U.S.G.S. 7.5 minute Strong City Quadrangle).
Figure 2. The trailer-mounted Giddings hydraulic soil probe used to collect cores in Fox Creek valley. values. Randomly selected replicates taken throughout the soil Radiocarbon (14C) Dating profile show precision better than 0.2‰. Stable carbon isotope values are reported relative to the Vienna PeeDee Belemnite Nine specimens, including four charcoal, two wood, one (VPDB) scale. peat, and two soil samples, were collected for radiocarbon Samples sent to the Stable-Isotope Biogeochemistry dating and submitted to the Illinois Geological Survey’s Isotope Laboratory at McMaster University were ground to a fine powder Geochemistry Section. The samples were decalcified and all and treated with 3M HCl for 12 hours in 50 ml polypropylene but two were assayed using atomic mass spectrometry (AMS). centrifuge tubes. The reacted sediment was then centrifuge and Two of the charcoal samples were large enough for conventional rinsed with 18.2Ω de-ionized water until neutrality was obtained. dating methods. The 14C ages were δ13C corrected and are The samples were then given a final centrifuge rinse with reported in radiocarbon years before present (14C yr B.P.) (Table acetone, decanted, and left to dry in an oven set at 60°C for 24 1). hours. After the samples were dried they were once again ground The two bulk soil samples collected for radiocarbon dating to a fine powder for isotopic analysis. The samples were run on came from a buried paleosol. The radiocarbon ages determined a continuous flow isotope ratio mass spectrometer (CF-IRMS). on soil carbon extracted from these samples are mean residence Samples were combusted in a Costech Elemental Combustion times for all organic carbon in the samples (see Campbell et System (Costech ECS 4010). The O.C. content of the decalcified al., 1967). Although mean residence time does not provide the samples was determined by the Costech element analyzer. absolute age of a buried soil, it does give a minimum age for the Separation of CO2 from N2 was done in a GC column. The period of soil development, and it provides a limiting age on the separated CO2 was then carried in a helium stream to the mass overlying material (Birkeland, 1999:137; Haas et al., 1986; Geyh spectrometer via a Conflo III. The mass spectrometer used was et al., 1975; Scharpenseel, 1975). the Finnegan Delta Plus XP, where the CO2 was measured and the results are reported in standard delta (δ) notation in permil (‰) with respect to VPDB for carbon. Sample reproducibility for these bulk sediment samples is <0.3 ‰.
Figure 3. Map showing the distribution of cores, sections, and Quaternary landforms in Fox Creek valley.
East Alluvial/Colluvial West Soil Fan Vertical GM Gunder Member Severance Fm. Scale (m) HCM Honey Creek Member 0 CCM Camp Creek Member 24,560 ± 350 LWA Late Wisconsin Alluvium 2 22,620 ± 340 4 T-1 GM HCM T-0a T-0b 2105± 25 GM 3530± 25 4520 ± 25 3570± 70 Permian HCM 4485 ± 30 Fox Creek CCM 11,220± 60 Limestone and Shale Peat LWA
Figure 4. Generalized cross-section of Fox Creek valley showing landforms, soil stratigraphy, lithostratigraphic units, and radiocarbon ages.
GEOMORPHOLOGY OF FOX CREEK VALLEY
Fox Creek flows south into the Cottonwood River and is a The T-0a surface is 1-2 m higher than T-0b and is separated third-order tributary according to Strahler’s stream classification from T-1 by a gently sloping 1 m-high scarp (Figure 4). There system (see Strahler, 1964). In much of the area where Fox are only small remnants of T-0a within the preserve, all within Creek flows through the preserve, its channel is against or near the northern segment of the valley (Figure 3). Although it is a the eastern valley wall (Figure 1). Consequently, Fox Creek component of the floodplain complex and prone to flooding, T-0a valley is asymmetrical within most of the preserve; the surface does not flood as frequently as T-0b. Also, unlike T-0b, T-0a is of the valley floor gently dips eastward towards the stream relatively flat and featureless. channel and is bounded by a steep valley wall on the eastern side The T-1 terrace dominates the valley floor of Fox Creek of the channel. A small segment of the channel crosses to the (Figure 3). This broad geomorphic surface has a 1-2 % slope and western side of the valley floor northeast of the Historic Ranch gently rises towards the valley wall where it either merges with Headquarters, and the channel shifts to the middle of the valley alluvial/colluvial fans (Figures 4 and 6), or is bounded by a steep floor about 625 m northwest of Strong City’s sewage disposal bedrock wall. With the exception of a few subtle swales marking ponds (Figure 1). the positions of paleo-channels, the T-1surface is featureless. The valley floor of Fox Creek is about 1,000 m wide and Large, low-angle alluvial/colluvial fans have formed where consists of four Quaternary landforms: a low floodplain (T-0b), some of the first and second-order drainage elements enter Fox a slightly higher floodplain (T-0a), an alluvial terrace (T-1), and Creek valley (Figures 3 and 4). Three of these fans have merged alluvial/colluvial fans (Figure 3). T-0b is the lowest geomorphic to form a bajada that parallels the valley wall from the Historic surface in the valley landscape (Figure 4) and is frequently Ranch Headquarters southward for about 2 km. As will be flooded. Its surface is characterized by prominent ridge and swale discussed later, the alluvial/colluvial fans contain fine and coarse- topography (Figure 5). The ridges are natural levees and the tops grained alluvium and colluvium derived from the uplands. of former point bars, and the swales mark the positions of flood chutes and paleo-channels.
Figure 5. Photograph of the T-0b surface. Note the ridge and swale topography.
Figure 6. View of the valley floor of Fox Creek looking west towards the Historic Ranch Headquarters. The Giddings soil probe is collecting Core 3 from the T-1 fill. STRATIGRAPHY AND ALLUVIAL CHRONOLOGY
The stratigraphy of Quaternary landform-sediment (mostly clay and silt) and generate few sand-size particles as they assemblages in Fox Creek valley was determined from 11 cores weather. Also, late-Pleistocene loess that probably mantled the and four cutbank exposures (Figure 3). Most of the effort was Flint Hills, but was stripped away by erosion during the Holocene directed towards the T-1 terrace because this landform composes (see Mandel et al., 2006), would have contributed a large quantity more than 75% of the valley floor. of silt but little sand to the Holocene alluvium in Fox Creek valley. T-1 Terrace At Section A (Figure 3) and adjacent Core 9, a buried soil (Soil 2) with Ak-Bk-BCk-CBk horizonation is 139 cm below the T-1 surface (Table 6 and 7 and Figure 10). Soil 2 is developed in Five cores (2, 3, 4, 6, and 9) were taken on the T-1 terrace in the Gunder Member, but like most buried soils associated with the NW 1/4 of Section 5, T.19 S., R.8 E., with four of these cores this unit of the DeForest Formation (see Bettis, 1995; Mandel and collected along an east-west transect (Figure 3). In addition, the Bettis, 2001a), it is not laterally traceable across the valley. T-1 fill was inspected at three cutbank localities (Sections A, B, The top stratum above Soil 2 consists of fine-grained and D). In cores 2, 3, 4, and 6, and at section D (Figure 3), the overbank deposits and also has characteristics typical of the upper 4-6+ m of the T-1 fill consists of moderately oxidized, fine- Gunder Member. This stratum is moderately oxidized and has grained overbank (flood) deposits typical of the Gunder Member been strongly modified by pedogenesis. The surface soil has of the DeForest Formation (Figures 7 and 8). The matrix color of well expressed A-Bt-Btk horizonation (Tables 6 and 7). The Bt soil and sediment below A or AB horizons and above Cg horizons horizon is 23 cm thick and is brown (10YR 4/3, dry) silty clay is brown (10YR 5/3-4/3, dry) and yellowish brown (10YR 5/4, loam. Films and threads of CaCO3 (stage I morphology) appear dry) (Figure 9 and Tables 2-7). However, reduced fine-grained at a depth of 61 cm and continue down through the Btk horizons. alluvium (Cg horizons) characterized by gray matrix colors is The Btk1 and Btk2 horizons have a combined thickness of 78 common near the bottom of the Gunder Member (Figure 9). cm and consist of brown (10YR 5/3, dry) and yellowish brown An abundance of organic matter, including plant macrofossils, (10YR 5/4, dry) silty clay loam, respectively. is indicated by unusually high organic carbon contents in Cg The Btk2 horizon of Soil 1 is welded to Soil 2. Soil welding, horizons (Table 8). The reduced, organic-rich alluvium that or “overprinting,” accounts for the films and threads of calcium often comprises the lower 1-2 m of the Gunder Member overlies carbonate in the Akb horizon. The Bk1b and Bk2b horizons gravelly lateral-accretion (channel) deposits mantling bedrock. are 76 cm thick and consist of brown (10YR 4/3-5/3, dry) silty The upper 2-3 m of the Gunder Member has been strongly clay loam with stage I carbonate morphology. In Section A and modified by pedogenesis. Surface soils developed on T-1 are Core 9, small fragments of charcoal and clumps of burned earth, Mollisols with well-expressed A-Bt or A-Bt-Btk horizonation probably representing a natural fire, were recorded at a depth (Tables 2-7). Core 3 contains a 45 cm-thick mollic epipedon (Ap of 225-230 cm, well within the Btkb horizon. Charcoal from + A horizon) with organic carbon contents ranging from 2.00 to this burn zone yielded an AMS radiocarbon age of 2105+25 1.57% (Table 8). Organic carbon contents remain high (1.50- yr B.P. (Figure 10). Based on this radiocarbon age, the rate of 0.86%) in the AB and upper Bt1 horizons, then steadily decrease sedimentation had decreased by ca. 2100 14C yr B.P., allowing with depth. Soil 2 to form soon after that time. The grain-size data for Core 3 indicate only a slight increase The bottom of Section A is at a depth of 250 cm below the in clay content across the boundary separating the A and Bt1 T-1 surface. Alluvial deposits below 250 cm were examined and horizon (Table 8). In fact, the grain-size distribution is fairly described in Core 9 (Table 6 and Figure 10). In Core 9, the Btk2b uniform from the lower 10 cm of the plow zone (Ap horizon) to horizon of Soil 2 is underlain by oxidized, yellowish brown a depth of 575 cm below the T-1 terrace. The highest proportions (10YR 5/4, dry) silty clay loam that has been slightly modified of clay are in the Bt2 horizon, with values ranging between 32.59 by soil development (BCkb horizon) (Table 7). There is even and 34.78 %. However, there is good evidence for clay illuviation less evidence of soil development in the CBkb horizon at a depth in the form of argillans (clay films) in the Bt horizons of the 390 to 610 cm. An abrupt change in soil color occurs at a depth surface soils developed in the T-1 fill. of 610 cm, with oxidized, yellowish brown (10YR 5/4, dry) silty The most striking aspect of the grain-size data for Core 3 is clay loam giving way to reduced, gray (5Y 5/1, dry) silty clay the paucity of sand (Table 8). Sand content is less than 3% to a loam composing the lower 1.9 m of the Gunder Member. Also, depth of 205 cm, then fluctuates between about 7 and 12% from an abrupt boundary separates the reduced portion of the Gunder 210 to 320 cm below surface. Even at depths between 320 and Member from dark gray (10YR 4/1, dry), peat-rich alluvium at a 580 cm, the sand content remains low, with most values ranging depth 800 cm. A peat sample collected at a depth of 800 to 810 between about 4 and 15%. The greatest sand content (34.67%) cm in Core 9 yielded an AMS radiocarbon age of 11,220+60 is at a depth of 600-605 cm in the 2C horizon. Even the gravel yr B.P. This radiocarbon age, combined with the stratigraphic below the thick package of vertical accretion deposits appears to record, indicates an unconformity at a depth of 8 m, with late have a relatively small sand component. Holocene alluvium overlying late Wisconsinan alluvium; the The low sand content of the T-1 fill is attributed to the early and middle Holocene alluvium was stripped out by stream primary source of the alluvium: shale and chert-rich limestone erosion. forming the Flint Hills. The shale and limestone are fine grained
10 Figure 7. Section D. Oxidized fine-grained alluvium composing the Gunder Member is exposed beneath the T-1 terrace.
Figure 8. Close-up of the Gunder Member exposed in Section D.
11 Based on the soil-stratigraphy observed in Section around 3500 14C years ago. At that time, rapid sedimentation was A and Core 9, sediments composing the top stratum probably occurring on the late Holocene floodplain, as indicated by the were deposited on the scarp and near-scarp area of the T-1 terrace unweathered, stratified alluvium in the lower 2 m of the Gunder during floods that submerged only the low, proximal portions Member. This interpretation is strongly supported by temporal of this geomorphic surface. The high, distal portions of the T-1 information gleaned from prehistoric cultural deposits (site terrace are isolated from low-magnitude floods and, therefore, did 14SC1340) 65 cm above the bed of charcoal-rich alluvium. not receive the top-stratum sediments. A portion of a bison vertebral column surrounded by charcoal A thick package of T-1 fill also is exposed in Section B, and burned earth (Feature 1) was recorded at a depth of 294-300 nearly 2 km south of Section A (Figures 3 and 11). A buried soil cm (Figures 12, 13, and 14). In addition, a large concentration of about 1 m below the T-1 surface probably is the same buried soil burned earth and charcoal (Feature 2) is 7.1 m east of Feature 1 (Soil 2) recorded in Section A and Core 9. The upper 4.5 m of the (Figures 15, 16, and 17). The top of Feature 2 is 290 cm below the T-1 fill consists of oxidized, fine-grained deposits typical of the T-1 surface. Gunder Member (Figures 11 and 12). The fine-grained alluvium Charcoal in direct contact with a vertebra (Figure 14) in is interbedded with gravel below a depth of 4.5 m. Feature 1 was collected and submitted for AMS dating. This A bed of charcoal-rich alluvium was recorded at a depth of sample yielded a radiocarbon age of 3530+25 yr B.P., which is 360-363 cm along the entire length of Section B. Wood charcoal statistically the same as the 14C age of 3570+70 yr B.P. determined recovered from this bed yielded a conventional radiocarbon on charcoal 65 cm below Feature 1. Together, these ages indicate age of 3570+70 yr B.P. The abundance of wood charcoal in the that rapid floodplain sedimentation was occurring around 3500 sediment suggests that a fire swept through the riparian forest 14C years ago. Also, the 14C age of the charcoal from Feature 1 indicates that at ca. 3500 yr B.P. Late Archaic people occupied the former floodplain (now the T-1 terrace) of Fox Creek. Feature 2 is 60 cm long, 25 cm thick, and mostly composed Top of Core of burned earth (Figure 17). Based on its stratigraphic position, this hearth-like feature is the same age as Feature 1. Many fine flecks of charcoal are scattered through the silty matrix of Feature 2, and a bulk sediment sample collected from the lower 10 cm of the feature yielded a small chert flake. Feature 2 dips to the east (Figure 16), conforming to the geometry of the underlying stratified floodplain deposits. These deposits are characterized by parallel, graded bedding (see the deposits below Feature 2 in Figure 16). The graded beds are sedimentation units characterized by a gradation in grain size, from coarser to finer sediment, upward from the base to the top of each unit. The graded beds are draped over a gravelly point bar; hence Feature 2 was close to the active channel of Fox Creek at ca. 3500 14C yr B.P. The charcoal and burned earth appear to have been splayed out by floodwaters that overtopped the point bar and deposited fine-grained alluvium above Feature 2. 4520 +– 25 The chronology of the T-1 fill in Fox Creek valley is inferred from radiocarbon ages determined on wood and peat collected from reduced sediments near the bottom of cores, and from charcoal recovered from natural burn zones and an archeological feature in the upper 4 m of the T-1 fill. Aggradation of the T-1 fill 4485 + 30 – was underway at ca. 11,200 14C yr B.P. and may have continued into the early Holocene. However, there is a gap in the alluvial record between ca. 11,200 and 4500 14C yr B.P. The early-through- middle Holocene appears to have been a period of net sediment removal on the valley floor of Fox Creek, a pattern detected among third-order and smaller streams throughout the Central Plains and Midwest (see Mandel, 1994c, 1995, 2006b; Bettis and Mandel, 2002). Sediment storage resumed during the late Holocene and was characterized by rapid floodplain sedimentation from ca. 4500 14C yr B.P. until sometime between ca. 3500 and 2100 14C yr B.P. By ca. 2100 14C yr B.P., sedimentation slowed, Figure 9. Core 3 taken on the T-1 terrace. Oxidized yellowish- and soil development was underway on the late Holocene 14 brown Gunder Member alluvium overlies reduced dark-gray floodplain soon after 2100 C yr B.P. There was another episode 14 Gunder Member alluvium. Gravel is at the bottom of the core. of floodplain sedimentation sometime after 2100 C yr B.P., The radiocarbon ages were determined on plant macro-fossils. resulting in burial of the soil only on the lowest portion of the T-1
12 . G Unit Strat
1 2 3 4 Soil Ap A AB Bt Bt Bt Bt BC CB C Cg 2C Horizons e 6 Cor . 2 1 Soil no . G Unit Strat + +
Soil 1 2 4520 25 4485 30 1 2 1 Ap A AB Bt Bt BC CB C1 C2 Cg Cg 2C Horizons T- e 3 Cor . 2 1 Soil no . G Unit Strat
+ + l
Soi 1, 220 60 2105 25 1 Ap A Bt Btk1 Btk2 Akb Bk1b Bk2b BCkb CBkb Cb Cg1b Cg2b Peaty Loam Horizons e 9 Cor . oil 1 S no nit HC U Strat.
Soil Ap A A Bw Bk1 Bk2 Akb Bwb BCb Cb 2Cb Horizons e
11 Cor . e oil 1 2 S no -0a T nit RC ts Creek Member U Strat.
at sample ood sample Pe W Rober
= Honey Creek Member = Gunder Member = = Charcoal sampl = = Soil G Ap A1 A2 AB Bw Ab1 ACb1 Cb1 Ab2 ACb2 C1b2 C2b2 2Cb2 RC HC Horizons e 5 Cor . oil 2 3 1 S no
h (cm) Dept
0 1 2 3 4 13 5 6 7 8 9 3, 5, 6, 9, and 11. 10. Stratigraphic columns for cores Figure Feature 1
Figure 11. Section B. Archeological Feature 1 associated with site 14SC1340 is 294 cm below the T-1 surface.
Feature 1
Figure 12. Close-up of Section B (site 14SC1340). The upper 4 m of the T-1 fill consist of oxidized, fine-grained alluvium (Gunder Member). Stratified gravel is at the bottom of the section. 14 terrace near the stream channel. However, the timing of this event is unknown. Sometime after ca. 2100 14C yr B.P. but before ca. 400 14C yr B.P., Fox Creek went through an episode of entrenchment, leaving its late Holocene floodplain as a terrace (T-1). This was followed by floodplain sedimentation forming the T-0a fill. The alluvial record preserved beneath the T-1 terrace of Fox Creek resembles the fluvial sequence at the Eureka site (14GR371) on the eastern edge of the Flint Hills in Greenwood County, Kansas (see Mandel, 2006b; Wambsgans, 2006). It also is remarkably similar to alluvial records in southern Kansas (see Mandel, 1995, 2006b) and the southern Great Plains (see Hall, 1990). At Eureka, three major episodes of fluvial activity were recorded (Mandel, 2006b). First, between ca. 4000 and 3000 14C yr B.P., approximately 6 m of alluvium accumulated on the late Holocene floodplain (now the T-1 terrace) of the upper Fall River. At localities throughout the southern Great Plains, rapid sedimentation occurred on floodplains between ca. 5000 and Feature 1 2000 yr B.P. Next, there was a ca. 1000 year period of decreased sedimentation rates, continuing to a period of landscape stability, soil development, and channel entrenchment. At the Eureka site, a buried soil near the top of the T-1 fill resembles the buried soil at Section A in Fox Creek valley and the Copan paleosol dated ca. 2000 to 1000 14C yr B.P. in southeastern Kansas and the Southern Plains (see Mandel, 1995, 2006b; Hall, 1990). These soils formed during slow alluviation, allowing for soil development. Finally, a period of resumed aggradation after ca. 1000 14C yr B.P. emplaced sediment on top of these soils.
Floodplain Complex (T-0a and T-0b)
Three cores – 1, 5, and 11 – were taken on the T-0a floodplain (Figure 3). In Core 1, a silty, 115 cm-thick top stratum that has been altered by pedogenesis (Soil 1) overlies a soil Figure 13. Bison vertebra being removed from the archeological (Soil 2) developed in silty alluvium. Soil 1 has a moderately Feature 1 in Section B (site 14SC1340). expressed A-Bw-Bk profile (Table 9). The mollic epipedon (Ap + A horizon) is 30 cm thick and consists of dark grayish brown (10YR 4/2, dry) silt loam. There is a brown (10YR 4/3, dry), Core 11, which was taken on the T-0a surface about 200 m silt-loam cambic (Bw) horizon above a Bk1 horizon with weak south of Core 1 (Figure 3), exposed a soil-stratigraphic sequence stage I carbonate morphology. The Bk1 and Bk2 horizons have identical to the one observed in Core 1 (Table 10). Yet there a combined thickness of 66 cm and consist of brown (10YR 4/3 are some differences between these cores. Specifically, the and 5/3, dry) silt loam. The Bk2 horizon is welded to Soil 2, as top stratum is thicker (160 cm) and the depth to gravel is less indicated by the threads of calcium carbonate and the prismatic (285 cm) in Core 11. Also, the gray (reduced), strongly mottled structure in the Akb horizon. alluvium observed in the lower part of Core 1 does not occur Soil 2 is 185 cm thick and has Ak-Bw-BC horizonation in the lower part of Core 11. Overall, the lithology and soil- (Table 9). The color and texture of Soil 2 is remarkably uniform stratigraphy of the alluvium in cores 1 and 11 indicate that most through most of the profile. The Akb and Bwb horizons consist of the T-0a fill is composed of the Honey Creek Member of the of dark grayish brown (10YR 4/2, dry) silt loam and brown DeForest Formation (Figure 4). However, Core 5, taken closer to (10YR 4/3, dry) silt loam, respectively. Brown (10YR 4/3, dry) the channel compared to cores 1 and 11, revealed that the Honey silt loam composes the BCb and Cb horizons, though a few thin Creek Member does not form all of the T-0a fill. beds of very dark gray (10YR 3/1, dry) silty clay loam occur in The upper 360 cm of Core 5 mostly consists of dark gray the Cb horizon. The fine-grained alluvium below a depth of 330 (10YR 4/1, dry) to dark grayish brown (10YR 4/2, dry) silty is dark gray (5Y 4/1, dry) clay loam with distinct yellowish red alluvium enriched with organic carbon. The surface soil has an (5YR 4/6, dry) mottles (Cgb horizon). The gray (reduced) matrix overthickened, cumulic A horizon and a brown (10YR 4/3, dry) color and reddish (oxidized) mottles are products of high and low cambic (Bw) horizon (Table 11 and Figure 10). Two buried soils ground-water levels, respectively. Stratified gravel was penetrated with weakly expressed A-AC profiles, are developed in the upper at a depth of 387 cm, and the core was terminated at a depth of 360 cm of the core: Soil 2 at a depth of 150-195 cm, and Soil 450 cm. 3 at a depth of 237-310 cm (Table 11 and Figure 10). Gravel
15 Bone
Bone
Figure 14. Close-up of archeological Feature 1 in Section B (site 14SC1340). Note the burned earth and charcoal beneath the bison bones.
Feature 1 Feature 2
Figure 15. Section B showing archeological features 1 and 2 at site 14SC1340. 16 Feature 2
Feature 2
Figure 16. Archeological Feature 2 in Section B (site Figure 17. Archeological Feature 2 in Section B (site 14SC1340). 14SC1340). The feature is 290-354 cm below the T-1 surface. Note the abundance of red and yellowish-red burned earth. The photo scale is 20 cm long. was penetrated at a depth 360 cm. The fine-grained alluvium in (Figure 20). The fine-grained alluvium is mostly dark grayish Core 5 resembles the Roberts Creek Member of the DeForest brown (10YR 4/2, dry) and brown (10YR 4/3, dry) silt loam Formation. In Fox Creek valley, this unit probably fills a late with little evidence of soil development. The presence of an A- Holocene channel cut into the Honey Creek Member. However, C soil profile at the top of the section is a good indicator of the additional coring is needed to clearly determine the stratigraphic youthfulness of the alluvium. The silty portion of the section is relationship of the Roberts Creek Member relative to the Honey interbedded with very dark grayish brown (10YR 3/2, dry) silty Creek Member. clay loam and brown (10YR 5/3, dry) loam and very fine sandy The lowest geomorphic surface in Fox Creek valley, T-0b, loam. Lenses of fine gravel are common in the lower 1 m of the was not cored because dense tree cover prohibited vehicle access fine-grained alluvium. (Figure 5). However, stream banks, including Section C (Figures A bed of charcoal-rich silt loam was recorded at a depth 3 and 18), provided opportunities to examine the T-0b fill. At the of 450-453 cm near the north end of Section C. Wood charcoal southern end of Section C, a veneer of stratified, fine-grained recovered from this bed yielded a conventional radiocarbon alluvium typical of the Camp Creek Member of the DeForest age of 2100+70 yr B.P. This is too old for the Camp Creek Formation mantles a thick unit of stratified gravel representing a Member, which typically is less than 400 years old (see Mandel former point bar (Figure 19). The surface soil developed in the and Bettis, 2001a). Therefore, the charcoal either originated Camp Creek Member is an Entisol with a thin A horizon above a from older alluvium and was redeposited with the Camp Creek C horizon. Member alluvium, or it is in Honey Creek or Gunder Member In most of Section C, a 3-5 m-thick unit of stratified, fine- alluvium truncated by the Camp Creek Member. Additional grained alluvium (Camp Creek Member) overlies stratified gravel radiocarbon dating is needed to resolve this problem.
17 Figure 18. Section C. The Camp Creek Member of the DeForest Formation is exposed beneath the T-0b surface (modern floodplain).
Figure 19. A portion of Section C. Stratified gravel composes a former point bar beneath the T-0b surface.
18 Alluvial/Colluvial Fans
Although the valley floor of Fox Creek is dominated by the T-1 terrace and floodplain complex (T-0a and T-0b), large, low-angle alluvial/colluvial fans are common on the western side of the valley floor, and fan remnants occur on the eastern side (Figure 3). Three cores – 7, 8, and 10 – were collected on a fan immediately southeast of the Historic Ranch Headquarters (Figures 3 and 21). Camp In Core 7, a 165 cm thick top stratum of fine-grained Creek alluvium interbedded with angular limestone and chert pebbles Member (colluvium) overlies a distinct paleosol (Figure 22). The surface soil has strongly expressed A-BA-Bt horizonation (Table 12). The mollic epipedon (Ap + A) is 38 cm thick and consists of dark grayish brown (10YR 4/2, dry) silty clay loam. Dark grayish brown silty clay loam in the BA horizon grades downward into silty clay comprising the Bt1 horizon. The argillic (Bt1-Bt4) horizon is 95 cm thick and has common, distinct, clay films. The hue of the soil matrix becomes redder with depth, ranging from 10YR in the Bt1, Bt2, and Bt3 horizons to 7.5YR in the Bt4 horizon. The Bt4 horizon is welded to the top of Soil 2, accounting for clay films and angular blocky structure in the Atb horizon. The buried paleosol (Soil 2) has well expressed At-Bt horizonation with strong morphological features, including prismatic structure and thick, continuous, dark brown (7.5YR 3/2, dry) clay films in the Btb horizon. The soil matrix of the Btb horizon is reddish brown (5YR 4/3, dry) (Figure 23) and there are few manganese oxide concretions. Angular pebbles representing colluvium are scattered through the paleosol. The frequency of these pebbles increases with depth, and gravelly silty clay (2Cb horizon) comprises the lower 10 cm of the core. The core was terminated in gravel at a depth of 200 cm. Figure 20. Section C. Note the stratified fine-grained alluvium The soil-stratigraphy in cores 8 and 10 is basically the same composing the Camp Creek Member beneath the T-0b flood as the soil-stratigraphy observed in Core 7 (Tables 13 and 14 plain. and Figure 24). However, the buried paleosol (Soil 2) in Core 8 is considerably thicker than the one in Core 7. Also, there are many manganese-oxide coatings in the Bt2b and BCtb horizons in Core 8.
19 Figure 21. Core 7 locality on the low-angle/colluvial fan. The Historic Ranch Headquarters is on the hill in the background. The view is to the northwest.
The upper 10 cm of the Atb in cores 7 and 8 were collected strong brown, yellowish brown, and/or reddish brown matrix for radiocarbon dating. Decalcified organic carbon from these colors; prismatic structure; iron and manganese oxide stains and samples yielded radiocarbon ages of 24,560+350 and 22,620+340 concretions; prominent clay films; and common macro-pores. The yr B.P., respectively. These ages are consistent with radiocarbon soils developed in the alluvial/colluvial fans in Fox Creek valley ages determined on soil carbon from the Severance formation in have all these characteristics. Based on the lithologic properties, northeastern Kansas and southeastern Nebraska (see Mandel and radiocarbon data and soil characteristrics, the large, low-angle Bettis, 2003a, 2003b). alluvial/colluvial fans in Fox Creek valley are composed of the As noted earlier, soils developed in the Severance formation Severance formation. typically have thick, well-expressed Bt horizons with brown,
20 Bottom of Core
Bottom of Core
22,620 +– 340
Figure 22. Core 8 taken on a low-angle alluvial/colluvial fan Figure 23. Core 8 after it was split open. Note the reddish-brown southeast of the Historic Ranch Headquarters. The radiocar- color of the Severance formation. bon age was determined on decalcified organic carbon from the upper 10 cm of a buried paleosol (Soil 2) developed in the Severance formation.
21 Depth (cm) Soil Core Soil Soil Core Soil Soil Core Soil no. 7 Horizons no. 8 Horizons no. 10 Horizons 0 1 1 1 Ap Ap Ap
25 A A A BA BA 50 BA Bt1
Bt1 Bt1 75 Bt2
Bt2 Bt3 100 Bt2 Bt3 Bt4
125 n 2 n 22, 620 + 340 n 2 Atb Bt4 Btb Atb n 150 2 n 24, 560 + 350 2Cb Atb
175 Btb Bt1b
Cb 200 = Soil sample
225 Bt2b
250
BCtb 275
2Cb 300
Figure 24. Stratigraphic columns for Cores 7, 8, and 10 taken on an alluvial/colluvial fan. 22 Figure 25. Map showing the Quaternary stratigraphic units in Fox Creek valley. 23 STABLE CARBON ISOTOPES
Stable carbon isotope analysis of organic carbon in soils is undesirable, but it should not significantly biasδ 13C has been successfully used in many paleoenvironmental studies interpretations because organic carbon contents of the older (e.g., Ambrose and Sikes 1991; Fredlund and Tieszen 1997; alluvium are low. Guillet et al., 1988; Kelly et al., 1991, 1993; Krishnamurthy et During periods of floodplain stability, organic carbon derived al., 1982; Nordt,1993, 2001; Nordt et al., 1994, 2001; Schwartz, from pedogenic processes is superimposed on, and mixed with, 1988; Schwartz et al., 1986). To understand the theory behind the inherited organic carbon fraction (Nordt, 2001). With the this analytical technique, the ecology of C3 and C4 plants must establishment of vegetation on floodplains, decaying organic 13 be considered. During photosynthesis, C4 plants discriminate matter accumulates in the soil and yield δ C signatures that are 13 less against CO2 than C3 plants (O’Leary 1981; Vogel 1980). in equilibrium with ambient vegetation conditions. This source This difference in carbon isotope fractionation results in a of organic carbon is desirable for reconstructing late Quaternary characteristic carbon isotope ratio in plant tissue that serves as an vegetation and climate (Nordt, 2001). 13 indicator for the occurrence of C3 and C4 photosynthesis (Nordt The δ C values determined at the University of Iowa’s Paul 1993:52). Boutton (1991a) demonstrated that the δ13C value of H. Nelson Isotope Laboratory for Core 3, which sampled the
C3 plant species range from -32 to -20‰, with a mean of -27‰, Gunder Member beneath the T-1 surface, illustrate the nature of 13 14 whereas the δ C values of C4 plant species range from -17 to vegetation change from ca. 4500 C yr B.P. to sometime after 14 -9‰, with a mean of -13‰. Thus, C3 and C4 plant species have ca. 2100 C yr B.P. (Figure 26). The bounding ages are based on distinct, non-overlapping δ13C values and differ from each other radiocarbon ages determined on plant macrofossils and charcoal by approximately 14‰ (Boutton, 1991b). from the bottom of Core 3 and the upper part of Section A, Nearly all trees, shrubs, forbs, and cool-season grasses respectively. The grain-size distribution, organic carbon content, are C3 species. Hence forests and most other temperate plant and radiocarbon ages suggest that sediment composing the lower communities are dominated by C3 species. Plants with the 2 m of the profile accumulated rapidly (Figure 26). Therefore, 13 C4 photosynthetic pathway are common in warm, semiarid variations in δ C values in this interval are probably influenced environments with high light intensity, such as grasslands, by shifts in detrital organic matter, rather than primarily savannas, deserts, and salt marshes. Studies have shown that reflecting changes in the contribution of standing vegetation to both the proportion of C4 species and the proportion of C4 soil organic matter. The abundance of woody plant macrofossils biomass in a given plant community are strongly related to in the reduced sediments below a depth of 4 m supports this environmental temperature (Boutton et al., 1980; Terri and Stowe, interpretation. 1976; Tieszen et al., 1979). These relationships are invaluable in Between about 400 and 150 cm below the T-1 surface, the 13 paleoecological studies when the relative proportions of C3 vs. C4 δ C values remain fairly consistent, ranging between -19.5 and species can be reconstructed (Nordt et al., 1994). -18.2‰ (Table 8). These values indicate a mixed C3/C4 plant
The carbon isotopic composition of plant litter changes community, though C4 plants composed 55-65% of the vegetative only slightly as it decomposes and is incorporated into soil cover. organic matter (Melillo et al., 1989; Nadelhoffer and Fry, 1988). There is a distinct shift to less negative δ13C values above
Consequently, the isotopic composition of soil organic matter 150 cm (Figure 26), which suggests that C4 vegetation increased reflects the dominant species (C3 vs. C4) in the plant community in abundance at the expense of C3 plant cover. The timing of this that contributed the organic matter (Dzurec et al., 1985; shift is unknown, but it probably occurred after ca. 2100 14C yr Nadelhoffer and Fry 1988; Stout and Rafter 1978). The stable B.P. This interpretation is based on a radiocarbon age of 2105+25 carbon isotopic composition of soil organic matter in surface and yr B.P. determined on charcoal 225 cm below the T-1 surface at buried soils may, therefore, be used to infer vegetation change Section A, not in Core 3. Regardless of the timing, the increase
(Hendy et al., 1972; Krishnamurthy et al., 1982; Nordt et al., in C4 vegetation may represent warmer (and possibly drier) 1994). Going one step further, stable carbon isotopic values may conditions and/or increased fire frequency, which would have be used to reconstruct climate. reduced woody plant cover in the valley. Organic carbon in the late Quaternary alluvial deposits and A dramatic excursion in δ13C values occurs within the upper soils in Fox Creek valley are derived primarily from two inherited 20 cm of the profile, with a shift towards a strongly negative sources and one pedogenic source. One inherited source is the value (Table 8 and Figure 26). This shift is a product of the brome erosion and redeposition of organic-rich material derived from grass, a C3 plant, recently introduced on the valley floor. the A horizons of upland soils. Because the Fox Creek basin The δ13C values for Core 3 and the core analyzed by encompasses an area that is bioclimatically and geologically Wambsgans (2006) at the Eureka site in Greenwood County uniform, organic carbon from upland soils reflects one set of are strikingly similar. At Eureka, carbon isotope values are paleoenvironmental conditions and not an average of several increasingly heavy (less negative) between ca. 3000 and 1000 climatic or vegetational zones as is the case with larger drainage 14C yr B.P., shifting from about -20‰ to 16‰. This shift reflects basins. This inherited organic source is, therefore, desirable for an increasing contribution of C4 vegetation. Wambsgans (2006) interpreting past vegetation and climatic shifts (Nordt, 2001). suggests that by ca. 1000 14C yr B.P., organic carbon preserved in
A second inherited source of organic carbon is older alluvium at Eureka had been contributed by 87% C4 vegetation alluvium that has been eroded and redeposited. This source and 23% C3 vegetation, the greatest C4 input of the past 3,500 years. 24 The comparative analysis of δ13C values for Core 3 noted earlier, the T-0a fill probably aggraded after ca. 21001 4C yr samples assayed at the University of Iowa’s Paul H. Nelson B.P. but before 400 14C yr B.P. The greatest fluctuations in the Isotope Laboratory and at McMaster University’s Stable-Isotope δ13C values occur in the lower 60 cm of the profile and probably Biogeochemistry Laboratory revealed remarkably similar curves reflect shifts in the input of detrital organic matter, similar to (Figure 27). Hence, the general trends in vegetation change what occurs in the lower 2 m of Core 3. Within the Akb horizon inferred from the δ13C values are represented in both data sets. of the buried soil, there is a distinct shift towards more negative However, in comparing the data sets, there is a 1-2‰ offset in δ13C values, suggesting that increased floodplain stability allowed 13 many of the δ C values. Given the consistency of the offset, this woody plants (C3 vegetation) to expand on the valley floor difference in values probably is a result of different sample pre- and perhaps on the adjacent uplands. However, the episode of treatment methods used by the two laboratories. Nevertheless, floodplain stability was followed by a period of instability and the 1-2‰ offset is significant in estimating the difference in the floodplain sedimentation that resulted in the burial of the Akb 13 ratio of vegetation type (C3 vs. C4) based on δ C values. Hence, horizon. This period of floodplain sedimentation is accompanied the specific reason for the 1-2‰ offset must be determined before by a distinct shift in δ13C values suggestive of an increase in vegetation ratios can be estimated with a high level of confidence. C4 vegetation. Again, such an increase in C4 vegetation may The δ13C values determined at McMaster University’s represent warmer (and possibly drier) conditions and/or increased Stable-Isotope Biogeochemistry Laboratory for Core 11 (Honey fire frequency. The dramatic shift towards more negativeδ 13C Creek Member beneath the T-0a surface) are presented in Table values in the upper 15 cm of the profile is a product of the brome 15 and illustrated in Figure 28. Unfortunately, the numerical age grass that was recently planted on the T-0a surface. of the alluvium comprising Core 11 is unknown. However, as
Figure 26. Diagram showing horiz onation, grain-size distribution, and depth function of δ13C and organic carbon for Core 3 (T-1 terrace.) 25 13 δ C (VPDB)
Univ. of Iowa
McMaster Univ.
Figure 27. Diagram comparing δ13C values determined on or- ganic carbon from Core 3. Samples were split and assayed at the University of Iowa’s Paul H. Nelson Stable Isotope Laboratory and at McMaster University’s Stable-Isotope Biogeochemistry Laboratory.
Figure 28. Diagram showing horizonation and depth function of δ13C and organic carbon for Core 11 (Honey Creek Member, T-Oa).
26 GEOARCHEOLOGY OF FOX CREEK VALLEY
The record of human occupation in the Flint Hills region archeological deposits dating to specific cultural periods are spans the past 11,500 years and may go further back in time. Yet likely to occur in the Fox Creek valley (Table 16). For example, few prehistoric sites have been recorded in the Tallgrass Prairie there is high geologic potential for buried Late Archaic and Early National Preserve, and only four had been recorded in Fox Creek Ceramic cultural deposits associated with the T-1 fill (Gunder valley prior to this investigation. The dense cover of brome grass Member) (Table 16). Most of the alluvium beneath the T-1 on the valley floor may have hindered detection of surface sites. terrace accumulated between ca. 4600 and 2000 14C yr B.P., and However, even though prehistoric cultural deposits probably at section A, a soil that developed soon after ca. 2100 yr B.P. occur at or near the land surface, it is likely that most of these is buried beneath a 139 cm-thick top stratum of fine-grained deposits date to the Ceramic periods because nearly all of the alluvium. A similar soil-stratigraphic sequence was observed at geomorphic surfaces composing the valley floor post-date 2000 Section B. 14 C years B.P. The results of the geoarcheological investigation The high geologic potential for buried Late Archaic cultural indicate that much of the archeological record, especially the deposits in the T-1 fill was realized at site 14SC1340, where two Late Archaic, will occur in a buried context. Chronological archeological features were recorded about 3 m below the T-1 information gleaned from cores and sections provides the basis surface. Charcoal associated with Feature 1 yielded a radiocarbon for locating buried prehistoric cultural deposits in Fox Creek age of 3530+25 yr B.P., which places it in the Late Archaic valley. period. As previously noted, alluvial and colluvial deposits of In addition to potential for buried Late Archaic and certain ages are preserved in Fox Creek valley, and these deposits Early Ceramic cultural deposits, the T-1 fill may harbor Early are associated with specific landforms. Recognizing the temporal Paleoindian cultural deposits, though this potential is ranked and spatial pattern of Holocene and late-Pleistocene sedimentary “moderate” because no terminal Pleistocene or early Holocene deposits has important implications for predicting the locations of soils were recorded beneath the T-1 surface (Table 16). Core 9 prehistoric cultural resources in the study area, and for explaining revealed that organic-rich late Wisconsinan alluvium underlies apparent gaps in the archeological record. late Holocene alluvium where Fox Creek cut deep into the In this study, determining the geologic potential for bedrock floor of the valley (Figure 4). Peat at a depth of 8 m buried cultural deposits in the valley landscape, as shown in yielded a radiocarbon age of 11,200+60 yr B.P.; hence, the Figure 29, considered the soil-stratigraphic record as well as alluvium adjacent to and possibly below the peat has geologic the temporal and spatial pattern of sedimentary deposits. The potential for containing Clovis cultural deposits. presence/absence of Holocene-age buried soils, especially buried The numerical age of the T-0a fill is unknown. However, A horizons, is important in the evaluation of geologic site- based on the alluvial chronology of the T-1 fill, the T-0a fill preservation potential (Mandel, 1992). Buried soils represent aggraded sometime after ca. 2000 14C yr B.P. Aggradation previous land surfaces that were stable long enough to develop was interrupted by at least one episode of landscape stability, recognizable soil profile characteristics (Mandel and Bettis, indicated by a weakly developed soil about 1.5 m below the T-0a 2001b). As Hoyer (1980) pointed out, if the probability of surface. Taking the soil-stratigraphy and estimated chronology human use of a particular landscape position was equal for each into account, the T-0a fill has high to moderate potential for year, it follows that the surfaces that remained exposed for the buried Early through Late Ceramic cultural deposits (Table 16). longest time would represent those with the highest probability Valley fill beneath the T-0b surface appears to be too young for containing cultural materials. Holocene-age buried soils to contain any in situ prehistoric cultural deposits (Table 16 and identified in the study area represent these surfaces, and evidence Figure 29). Although the numerical age of the T-0b fill has not for human occupation would most likely be associated with been determined, it consists of stratified Camp Creek Member them. However, prehistoric cultural deposits, even rich ones, deposits that typically are less than 400 years old and often less also may be found in sediment that has not been modified by than 200 years old in eastern Kansas. soil development (Hoyer, 1980; Mandel and Bettis, 2001b). The alluvial/colluvial fans examined on the margin of the The discovery of archeological features in stratified alluvium valley floor have low geologic potential for containing buried (non-soil) at site 14SC1340 (Section B) is a case in point. cultural deposits (Table 16 and Figure 29). Organic carbon from Hence the presence/absence of buried soils cannot be used as buried soils developed in the Severance formation composing the sole criterion for evaluating the potentials for buried cultural these fans yielded radiocarbon ages of ca. 24,600 and 22,500 materials. The mere presence of Holocene deposits beneath a yr B.P. The age of the top stratum mantling the buried soils geomorphic surface offers potential for buried cultural materials. is unknown, but the magnitude of surface-soil development Going one step further, geomorphic, chronostratigraphic, suggests that the fans have been relatively stable for the past and soil-stratigraphic data were used to predict where buried 12,000 years. Based on the available data, the large, low-angle
27 Figure 29. Map showing the geologic potential for buried prehistoric cultural deposits in Fox Creek valley.
28 alluvial/colluvial fans in Fox Creek valley can only contain valley removed most if not all Early and Middle Archaic cultural buried Pre-Clovis cultural deposits, and that potential is ranked deposits that may have been associated with the alluvium. During low because of the great antiquity of these landforms and the the late Holocene, beginning around 4500 14C yr B.P., alluvium paucity of North American sites pre-dating the Clovis period. accumulated in Fox Creek valley and Late Archaic cultural This study has yielded new information that helps deposits were deeply buried. address the following archaeological questions. Why have no In sum, the material remains of human occupation in Fox archeological sites dating to the warm, dry Altithermal (ca. Creek valley have passed through a geologic filter to become the 8000 - 5000 14C yr B.P.) been documented in Fox Creek valley? archeological record. Understanding the nature of the temporal Were people living on the uplands or in other regions during this and spatial patterns that this filter imposed on the archeological period? Also, why have few Late Archaic sites been recorded record is the first task in identifying archeological patterns that in the valley? This study indicates that geologic processes have reflect human choices (Bettis and Mandel, 2002; Mandel, 2006b). affected the archeological record by removing portions of it The geoarchaeological investigation accomplished this task, but and burying others. Specifically, during the early and middle the predictive model presented here remains to be tested. Holocene, erosion and net transport of alluvium in Fox Creek
RECOMMENDATIONS FOR FUTURE RESEARCH
Additional investigations would further develop our radiocarbon ages of the valley fills are firmly established, and the understanding of late-Quaternary landscape evolution and local variation of δ13C values is better understood, stable carbon environmental change in Fox Creek valley and the surrounding isotope profiles could be used as a correlation aid for linking region. Specific research needs are presented below. localities together and for evaluating the time span represented Future research should focus on gaining a better by stratigraphic sections. Also, δ13C analyses of soil and sediment understanding of the alluvial chronology of the Holocene valley samples from similar-age alluvial deposits in adjacent stream fills in Fox Creek valley. In addition to refining the temporal valleys, such as Palmer Creek, is needed to determine whether a aspects of late Holocene landscape evolution, a well-defined regional bioclimatic signal is represented in the δ13C record. chronology would provide a more precise record of vegetative The available stable carbon isotope data suggest that after change as recorded in the δ13C values of organic carbon and in ca. 4500 14C yr B.P., prairie expanded and tree cover declined other bioclimatic indices. in Fox Creek valley. The composition of the prairie may have Although radiocarbon ages have been determined on fluctuated during this period in response to climatic perturbations. materials from the bottom and middle portions of the T-1 fill, Two lines of evidence preserved in the sedimetological record and it is apparent that T-1 aggradation slowed around 2100 14C should be pursued to determine whether such compositional yr B.P., the time at which most of the T-1 surface stabilized is fluctuations occurred: plant macrofossils and phytoliths. unknown. Also, the numerical age of the top stratum at sections The deep cores on the T-1 terrace revealed that plant A and B is unknown. Hence, there is uncertainty about when Soil macrofossils are abundant in the reduced sediments composing 2 was buried at these localities on low portions of the T-1 terrace. the lower part of the Gunder Member. Baker et al. (2000) Furthermore, the numerical ages of the T-0a and T-0b fills are demonstrated that identification of the plant macrofossils, unknown. Refinement of the late Holocene alluvial chronology combined with radiocarbon dating of the plant remains, is a will require additional coring and inspection of cutbank powerful tool for reconstructing vegetative change in a small exposures so as to recover 14C-dateable material. drainage basin. This information can, in turn, be used to The δ13C values for cores 3 and 11 demonstrate the potential reconstruct regional climate, especially when it is combined with for stable carbon isotope analysis to provide information on the isotopic data. general characteristics of past vegetative cover (proportion of C3 Opal phytoliths preserved in the valley fills should be vs. C4 cover) in Fox Creek valley and the drainage basin. Several analyzed to determine whether there have been significant issues important to interpretation of these data can be addressed changes in the composition of the tallgrass prairie during the with further δ13C analyses. To accurately interpret the isotopic late Holocene. It is likely that phytoliths are well preserved in values in terms of standing vegetation, and thereby infer regional the T-1, T-0a, and T-0b fills, and cores taken for δ13C analysis climatic change, it is important to understand the nature of local of organic carbon should be processed to recover these plant variability of isotopic composition of the soil organic carbon. microfossils. Phytolith assemblages in soil and sediment samples Vegetation varies across the landscape, and we must therefore can be analyzed to determine the proportion of chloridoid, have a better understanding of how this variation translates panicoid, and festucoid types. The festucoid class of phytoliths is 13 into variations in buried organic carbon. This will require δ C associated with the C3 grasses, the chloridoid class is associated analyses of soil and sediment samples from a larger suite of with the more arid, warm weather C4 grasses, and the panicoid cores collected across the valley landscape. Once the bounding class is associated with the warm weather, more humid C4
29 grasses, such as Paniceae and Andropogoneae (Twiss, 1983). products of regional environmental changes, the phytolith record Hence, an analysis of phytolith assemblages in radiocarbon- can be used to reconstruct late-Holocene bioclimates of the Flint dated stratigraphic sequences can shed light on changes in prairie Hills region. composition through time. Because these changes are often
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33 Martin, C.W., 1993, radiocarbon ages on late Pleistocene loess central Texas based on isotopic composition of organic stratigraphy of Nebraska and Kansas, central Great carbon: Quaternary Research, v. 41, p. 109-120. Plains, U.S.A.: Quaternary Science Reviews, v. 12, p. O’Leary, M., 1981, Carbon isotope fractionation in plants: 179-188. Phytochemistry, v. 20, p. 553-567. Mason, J.A., Bettis, E.A., III, Roberts, H.M., Muhs, D.R., and Pye, K., Winspear, N.R., and Zhou, L.P., 1995, Joeckel, R.M., 2006, AMQUA pre-meeting field trip Thermoluminescence ages of loess and associated no. 1: Last Glacial loess sedimentary system of eastern sediments in central Nebraska, U.S.A.: Paleogeography, Nebraska and western Iowa; in, Guidebook for Field Paleoclimatology, and Palaeoecology, v. 118, p. 73-87. Trips, 18th Biennial Meeting of the American Quaternary Reed. E.C., and Dreeszen, V.H., 1965, Revision of the Association, R.D. Mandel, ed.: Kansas Geological classification of the Pleistocene deposits of Nebraska: Survey Technical Series, p. 1-1 – 1-22. Lincoln, Nebraska Conservation and Survey Division, May, D. W., and Holen, S. R., 1993, Radiocarbon ages of soils University of Nebraska, Bulletin 23, 65 p. and charcoal in late Wisconsinan Loess, south-central Scharpenseel, H. W., 1975, Radiocarbon dating of soils - Nebraska: Quaternary Research, v. 39, p. 55-58. problems, troubles, hopes; in, Paleopedology: Origin, Melillo, J.M., Aber, J.D., Linkins, A.E., Ricca, A., Fry, B., and Nature, and Dating of Paleosols, D. H. Yaalon, ed.: Nadelhoffer, K.J., 1989, Carbon and nitrogen dynamics Jerusalem, Israel University Press, p. 77-88. along the decay continuum: plant litter to soil organic Schultz, C.B., and Stout, T.M., 1945, Pleistocene loess deposits matter: Plant and Soil, v. 115, p. 189-198. of Nebraska: American Journal of Science, v. 243, p. Morrison, R.B., 1987, Long-term perspective: changing rates 231-244. and types of Quaternary surficial processes: erosion- Schultz, C.B., and Tanner, L.G., 1957, Medial Pleistocene fossil deposition-stability cycles; in, Geomorphic Systems vertebrate localities in Nebraska: Lincoln, University of of North America, W.L. Graf, ed.: Boulder, Colorado, Nebraska, State Museum Bulletin, v. 4, p. 59-81. Geological Society of America, Decade of North Schwartz, D., 1988, Some Podzols on Bateke sands and their American Geology Centennial Special Volume 2, p. origin, People’s Republic of Congo: Geoderma, v. 43, p. 167-176. 229-247. Muhs, D.R., Swinehart, J.B., Loope, D.B., Aleinikoff, J.N., Schwartz, D., Mariotti, A., Lanfranchi, R., and Guillet, B., 1986, and Been, J., 1999, 200,000 years of climate change 13C/12C ratios of soil organic matter as indicators of recorded in eolian sediments of the High Plains of vegetation changes in the Congo: Geoderma, v. 39, p. eastern Colorado and western Nebraska; in, Colorado 97-103. and Adjacent Areas, D.R. Lagrson, A.P. Lester, and B.D. Self, H., 1978, Environment and Man in Kansas. Lawrence, Trudgill, eds.: Boulder, Colorado, Geological Society of Regents Press of Kansas, 288 p. America Field Guide 1, p.71-91. Soil Survey Division Staff, 1993, Soil survey manual, U.S. Nadelhoffer, K.F. and Fry, B., 1988, Controls on natural nitrogen- Department of Agriculture Handbook No. 18: 15 and carbon-13 abundance in forest soil organic Washington, D.C., U.S. Government Printing Office, matter: Soil Science Society of America Journal v. 52, p. 437 p. 1633-1640. Soil Survey Division Staff, 1996, Soil survey manual, U.S. Nordt, L.C., 1993, Additional geoarcheological investigations Department of Agriculture Handbook No. 21: at the Fort Hood military reservation, Ft. Hood, Texas: Washington, D.C., Government Printing Office, 523 p. Ft. Hood, Archeological Resource Management Series Strahler, A.N., 1964, Quantitative geomorphology of drainage Research Report No. 28 (addendum to Research Report basin and channel networks; in, Handbook of Applied no. 25), United States Army. Hydrology, V.T. Chow, ed.: New York, McGraw-Hill, p. Nordt, L.C., 2001, Stable carbon and oxygen isotopes in 39-76. soils; in, Earth Science in Archaeology, P. Goldberg, Stout, J.D., and Rafter, T.A., 1978, The 13C/12C isotopic ratios of V.T. Holliday, and C.R. Ferring, eds.: Norwell, some New Zealand Tussock grassland soils; in, Stable Massachusetts, Kluwer Academic/Plenum, p. 419-448. Isotopes in the Earth Sciences, B.W. Robinson, ed.: Nordt, L.C., Boutton, T.W., Hallmark C.T., and Waters, M.R., Wellington, New Zealand, DSIR Bulletin 220, p. 75-83 1994, Late Quaternary vegetation and climate change in Terri, J.A., and Stowe, L.G., 1976, Climatic pattern and the
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35 36 APPENDIX Tables
Table 1. Radiocarbon ages determined on samples from Fox Creek valley. ______Sample Material Depth Strat. 14C Age δ13C Laboratory Locality Assayed (cm) Landform Unit1 (yr B.P.) (o/oo) Number ______Section C Charcoal 450-455 T-0a CC? 2100+25 -25.4 ISGS-5928 Section A Charcoal 225-226 T-1 HC 2105+25 -26.0 ISGS-A0695 Section B Charcoal2 294-295 T-1 GM 3530+25 -25.2 ISGS-A0696 Section B Charcoal 360-361 T-1 GM 3570+70 -27.3 ISGS-5927 Core 3 Wood 480-485 T-1 GM 4520+25 -26.0 ISGS-A0701 Core 3 Wood 525-530 T-1 GM 4485+30 -25.2 ISGS-A0702 Core 9 Peat 800-810 T-1 LWA 11,220+60 -17.6 ISGS-A0712 Core 8 DSC3 124-134 A/CF4 SV 22,620+340 -15.5 ISGS-A0711 Core 7 DSC 147-157 A/CF SV 24,560+350 -15.9 ISGS-A0713 ______1Stratigraphic Units: HC=Honey Creek Member; GM=Gunder Member; LWA=Late Wisconsin Alluvium; SV=Severance Formation 2The charcoal sample was collected from Feature 1 associated with site 14SC1340 at Section 2. 3DSC=Decalcified soil carbon 4A/CF=Alluvial/colluvial fan
Table 2. Description of Core 2. ______Sediment: Alluvium Slope: 1% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Gunder Member 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary. 20-30 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; very weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 30-45 AB Brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure parting to moderate medium and coarse granular; friable; common fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 45-80 Bt1 Brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to weak fine subangular blocky; slightly hard; common thin distinct nearly continuous dark grayish brown (10YR 4/2) clay films on ped faces; common fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 80-146 Bt2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure parting to moderate fine subangular blocky; slightly hard; common thin distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 146-180 Btk1 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure parting to moderate fine subangular blocky; slightly hard; common thin distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine threads of calcium carbonate; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 180-305 Btk2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to weak fine subangular blocky; hard; few thin distinct patchy dark grayish brown (10YR 4/2) clay films on ped faces; few dark grayish brown (10YR 4/2) clay flows in macro-pores; few fine threads of calcium carbonate; few fine and very fine roots; few worm casts and open worm burrows;
37
Table 2 continued. ______Sediment: Alluvium Slope: 1% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Gunder Member few fine flecks of charcoal; common lenses of granules and fine pebbles; common fine and very fine pores; gradual boundary 305-360 BC Yellowish brown (10YR 5/4) silty clay loam to clay loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure; firm; many lenses of granules and fine pebbles; common fine and very fine pores; abrupt boundary. 360-378 C Light olive brown (2.5Y 5/3) clay loam, olive brown (2.5Y 4/3) moist; massive; firm; many granules and pebbles scattered through the matrix; few fine and very fine pores; gradual boundary. 378-395 Cg1 Laminated gray (5Y 5/1) silty clay loam and clay loam, dark gray (5Y 4/1) moist; massive; firm; interbedded with fine gravel; few fine and very fine pores; abrupt boundary. 395-420 Cg2 Laminated greenish gray (10Y 5/1) silty clay loam, dark greenish gray (5Y 4/1) moist; massive; firm; interbedded with fine gravel; few shell fragments; few fine and very fine pores; abrupt boundary. 420-440 Cg3 Laminated gray (10YR 5/1) silty clay loam, dark gray (10YR 4/1) moist; common fine prominent strong brown (7.5YR 4/6), yellowish red (5YR 4/6), and red (2.5YR 4/6) mottles; massive; firm; interbedded with fine gravel; few shell fragments; few fine and very fine pores; gradual boundary. 440-512 Cg4 Laminated dark gray (10YR 4/1) silty clay loam, very dark gray (10YR 3/1) moist; massive; firm; common thin beds of plant macro-fossils; abrupt boundary. 512-520+ 2C Coarse gravel; refusal at 520 cm. ______
Table 3. Description of Core 3. ______Landform: T-1 Sediment: Alluvium Slope: 1% Drainage: Well drained Remarks: Plant macro-fossils collected at depths of 480-485 cm and 525-530 cm yielded AMS radiocarbon ages of 4520+25 yr B.P. and 4485+30 yr B.P., respectively. ______Depth Soil (cm) Horizon Description ______Gunder Member 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary. 20-45 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; very weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 45-60 AB Brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure parting to moderate medium and coarse granular; friable; common fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 60-120 Bt1 Brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to weak fine subangular blocky; slightly hard; common thin distinct continuous dark grayish brown (10YR 4/2) clay films on ped faces; common fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
38 Table 3 continued. ______Landform: T-1 Sediment: Alluvium Slope: 1% Drainage: Well drained Remarks: Plant macro-fossils collected at depths of 480-485 cm and 525-530 cm yielded AMS radiocarbon ages of 4520+25 yr B.P. and 4485+30 yr B.P., respectively. ______Depth Soil (cm) Horizon Description ______Gunder Member 120-170 Bt2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure parting to moderate fine subangular blocky; slightly hard; common thin distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 170-210 BC Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure; slightly hard; few fine and very fine roots; common granules; few fine and very fine pores; gradual boundary. 210-235 CB Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure; slightly hard; few fine and very fine roots; common granules and pebbles; few fine and very fine pores; gradual boundary. 235-260 C1 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; massive; firm; many granules and pebbles; few fine and very fine pores; gradual boundary. 260-395 C2 Brown (10YR 5/3-4/3) silty clay loam, dark yellowish brown (10YR 4/4) moist; massive; firm; many granules and pebbles; few fine and very fine pores; gradual boundary. 395-460 Cg1 Laminated gray (10YR 5/1) silty clay loam interbedded with loam, dark gray (10YR 4/1) moist; common fine prominent strong brown (7.5YR 4/6) and yellowish red (5YR 4/6) mottles; massive; firm; interbedded with fine gravel; few fine and very fine pores; abrupt boundary. 460-570 Cg2 Laminated dark gray (10YR 4/1) silty clay loam, very dark gray (10YR 3/1) moist; massive; firm; common thin beds of plant macro-fossils; interbedded with granules and fine gravel; abrupt boundary. 570-600 2C Gravel; refusal at 600 cm. 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary. 20-37 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; very weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 37-47 AB Brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure parting to moderate medium and coarse granular; friable; common fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 47-76 Bt1 Brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; moderate medium prismatic structure parting to weak fine subangular blocky; slightly hard; common distinct continuous dark grayish brown (10YR 4/2) clay films onped faces; common fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 76-130 Bt2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to weak fine subangular blocky; hard; few distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 130-248 Bt3 Yellowish brown (10YR 5/4) light silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to weak fine subangular blocky; hard; few distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine and very fine roots; common fine and very fine pores; gradual boundary. 248-289 BCk Yellowish brown (10YR 5/4) silt loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure; hard; few fine films and threads of calcium carbonate; many fine and very fine pores; abrupt boundary. 289-330 2C Stratified chert-rich gravel; refusal at 330 cm. ______
39 Table 4. Description of Core 4. ______Landform: T-1 Sediment: Alluvium Slope: 1% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Gunder Member 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary. 20-37 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; very weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 37-47 AB Brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure parting to moderate medium and coarse granular; friable; common fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 47-76 Bt1 Brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; moderate medium prismatic structure parting to weak fine subangular blocky; slightly hard; common distinct continuous dark grayish brown (10YR 4/2) clay films on ped faces; common fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 76-130 Bt2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to weak fine subangular blocky; hard; few distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 130-248 Bt3 Yellowish brown (10YR 5/4) light silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to weak fine subangular blocky; hard; few distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine and very fine roots; common fine and very fine pores; gradual boundary. 248-289 BCk Yellowish brown (10YR 5/4) silt loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure; hard; few fine films and threads of calcium carbonate; many fine and very fine pores; abrupt boundary. 289-330 2C Stratified chert-rich gravel; refusal at 330 cm. ______
40 Table 5. Description of Core 6. ______Landform: T-1 Sediment: Alluvium Slope: 1% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Gunder Member 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary.
20-32 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; very weak fine subangular blocky structure parting to weak fine granular; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary.
32-42 AB Brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure parting to moderate medium and coarse granular; friable; common fine and very fine roots; many worm casts and open worm burrows; gradual boundary.
42-80 Bt1 Brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to weak fine subangular blocky; slightly hard; common thin distinct nearly continuous dark grayish brown (10YR 4/2) clay films on ped faces; common fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
80-150 Bt2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure parting to moderate fine subangular blocky; slightly hard; common thin distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
150-260 Btk1 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure parting to moderate fine subangular blocky; slightly hard; common thin distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine threads of calcium carbonate; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
260-310 Btk2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to weak fine subangular blocky; hard; few thin distinct patchy dark grayish brown (10YR 4/2) clay films on ped faces; few dark grayish brown (10YR 4/2) clay flows in macro-pores; few fine threads of calcium carbonate; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
310-370 BC Yellowish brown (10YR 5/4) silty clay loam to clay loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure; firm; common fine and very fine pores; abrupt boundary.
370-450 CB Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure; slightly hard; few fine and very fine pores; gradual boundary.
450-555 C Light olive brown (2.5Y 5/3) clay loam, olive brown (2.5Y 4/3) moist; massive; firm; common granules and few lenses of pebbles; few fine and very fine pores; gradual boundary.
555-590 Cg Laminated gray (5Y 5/1) silty clay loam and clay loam, dark gray (5Y 4/1) moist; massive; firm; interbedded with fine gravel; few fine and very fine pores; abrupt boundary.
590-620+ 2C Coarse gravel; refusal at 620 cm. ______
41 Table 6. Description of Section A. ______Landform: T-1 Sediment: Alluvium Slope: 1% Drainage: Well drained Remarks: Charcoal fragments collected at a depth of 225-230 cm yielded an AMS radiocarbon age of 2100+25 yr B.P. ______Depth Soil (cm) Horizon Description ______Gunder Member 0-20 Ap Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; clear smooth boundary.
20-38 A Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual smooth boundary.
38-61 Bt Brown (10YR 4/3) light silty clay loam, dark brown (10YR 3/3) moist; weak fine prismatic structure parting to weak fine subangular blocky; firm; common thin discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; common fine and very fine roots; many worm casts and open worm burrows; common fine and very fine pores; gradual smooth boundary.
61-96 Btk1 Brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; weak medium prismatic structure parting to moderate fine subangular blocky; firm; common thin discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few films and threads of calcium carbonate; common fine and few medium roots; common worm casts and open worm burrows; common fine and very fine pores; gradual smooth boundary.
96-139 Btk2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to moderate fine subangular blocky; firm; few thin patchy dark grayish brown (10YR 4/2) clay films on ped faces; common films and threads of calcium carbonate; common fine and few medium roots; few worm casts and open worm burrows; many fine and very fine pores; clear smooth boundary.
139-174 Akb Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to moderate fine and medium granular; friable; many films and threads of calcium carbonate; few fine and medium roots; many very fine and fine pores; gradual smooth boundary.
174-204 Bk1b Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak medium prismatic structure parting to weak fine subangular blocky; friable; many encrusted threads and few fine soft concretions of calcium carbonate; few fine and medium roots; many fine and very fine pores; gradual smooth boundary.
204-250 Bk2b Brown (10YR 5/3) silt loam, brown (10YR 4/3) moist; very weak fine subangular blocky structure parting to very weak very fine subangular blocky; friable; few fine threads of calcium carbonate; few small fragments of charcoal at a depth of 225 cm; few fine roots; common fine and very fine pores. ______
42 Table 7. Description of Core 9. ______Landform: T-1 Sediment: Alluvium Slope: 1% Drainage: Well drained Remarks: Peat collected at a depth of 800-810 cm yielded an AMS radiocarbon age of 11,220+60 yr B.P. ______Depth Soil (cm) Horizon Description ______Gunder Member 0-20 Ap Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary. 20-38 A Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary. 38-61 Bt Brown (10YR 4/3) light silty clay loam, dark brown (10YR 3/3) moist; weak fine prismatic structure parting to weak fine subangular blocky; firm; common thin discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; common fine and very fine roots; many worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 61-96 Btk1 Brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; weak medium prismatic structure parting to moderate fine subangular blocky; firm; common thin discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few films and threads of calcium carbonate; common fine and few medium roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 96-139 Btk2 Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to moderate fine subangular blocky; firm; few thin patchy dark grayish brown (10YR 4/2) clay films on ped faces; common films and threads of calcium carbonate; common fine and few medium roots; few worm casts and open worm burrows; many fine and very fine pores; clear boundary. 139-174 Akb Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to moderate fine and medium granular; friable; many films and threads of calcium carbonate; few fine and medium roots; many very fine and fine pores; gradual boundary. 174-204 Bk1b Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak medium prismatic structure parting to weak fine subangular blocky; friable; many encrusted threads and few fine soft concretions of calcium carbonate; few fine and medium roots; many fine and very fine pores; gradual boundary. 204-250 Bk2b Brown (10YR 5/3) silt loam, brown (10YR 4/3) moist; very weak fine subangular blocky structure parting to very weak very fine subangular blocky; friable; few fine threads of calcium carbonate; few small fragments of charcoal at a depth of 225 cm; few fine roots; common fine and very fine pores; gradual boundary. 250-350 BCkb Brown (10YR 5/3) to yellowish brown (10YR 5/4) silt loam, brown (10YR 4/3) to dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure parting to very weak very fine subangular blocky; friable; few fine threads of calcium carbonate; common fine and very fine pores; gradual boundary. 350-390 CBkb Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; very weak fine subangular blocky structure parting to very weak very fine subangular blocky; firm; few fine threads of calcium carbonate; common fine and very fine pores; gradual boundary. 390-610 Cb Yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; common fine distinct yellowish brown (10YR 5/6) and strong brown (7.5YR 4/6) mottles; massive; firm; common fine and very fine pores; abrupt boundary. 610-730 Cg1b Gray (5Y 5/1) silty clay loam, dark gray (5Y 4/1) moist; few fine faint light olive brown (2.5Y 5/4) mottles; massive; firm; common fine and very fine pores; gradual boundary. 730-800 Cg2b Laminated gray (5Y 6/1) and dark gray (5Y 5/1) silty clay loam, dark gray (5Y 5/1) and very dark gray (5Y 3/1) moist; few fine faint light olive brown (2.5Y 5/4) mottles; massive; firm; common fine and very fine pores; abrupt boundary. 800-820 Cg3b Dark gray (10YR 4/1) loam, very dark gray (10YR 3/1) moist; massive; firm; common lenses of peat. ______43 Table 8. Grain-size distribution, δ13C values, and organic carbon content for Core 3.
Grain-Size Distribution Soil Total Coarse Fine Total Total Organic Depth Horizon Sand Silt Silt Silt Clay Texture δ13C (‰) Carbon (cm) % % % % % (%) 0- 5 Ap 2.63 49.98 20.13 70.11 27.26 SiCL -23.3 2.00 10- 20 Ap 2.12 46.39 18.75 65.14 32.75 SiCL -16.7 1.72 20- 25 A 1.58 45.28 20.87 66.15 32.28 SiCL -14.5 1.62 30- 35 A 1.46 57.18 9.73 66.91 31.63 SiCL -14.5 1.57 40- 45 AB 1.63 41.16 25.24 66.40 31.98 SiCL -14.1 1.50 50- 55 AB 1.38 42.41 23.46 65.87 32.76 SiCL -14.4 1.29 70- 75 Bt1 0.94 37.42 26.28 63.70 35.37 SiCL -15.2 1.12 80- 85 Bt1 0.83 38.41 27.45 65.86 33.31 SiCL -15.9 0.94 90- 95 Bt1 0.77 40.31 24.97 65.28 33.95 SiCL -17.1 0.86 100-105 Bt1 0.65 37.62 27.04 64.66 34.69 SiCL -16.6 0.73 110-115 Bt1 0.73 41.50 25.41 66.91 32.36 SiCL -17.0 0.63 120-125 Bt2 0.80 39.43 25.92 65.35 33.85 SiCL -18.0 0.61 130-135 Bt2 0.99 41.69 24.73 66.42 32.59 SiCL -18.0 0.54 140-145 Bt2 1.06 34.78 30.70 65.48 33.45 SiCL -17.6 0.46 150-155 Bt2 1.05 41.88 22.29 63.51 34.78 SiCL -18.4 0.48 160-165 Bt2 0.99 41.17 23.52 64.69 34.32 SiCL -18.9 0.48 170-175 BC 0.89 38.43 26.37 64.80 34.31 SiCL -19.0 0.47 180-185 BC 1.05 39.31 24.82 64.13 34.83 SiCL -19.2 0.43 190-195 BC 1.47 38.79 24.01 62.80 35.73 SiCL -19.0 0.39 200-205 BC 2.85 37.10 23.02 60.12 37.02 SiCL -18.9 0.38 210-215 CB 7.29 31.60 26.55 58.15 34.56 SiCL -18.7 0.36 220-225 CB 9.64 27.96 27.91 55.87 34.49 SiCL -19.5 0.37 230-235 CB 11.39 29.72 24.28 54.00 34.64 SiCL -18.5 0.32 240-245 C1 8.79 31.44 26.20 57.64 33.57 SiCL -18.5 0.34 250-255 C1 11.56 27.99 25.76 53.75 34.69 SiCL -19.0 0.35 260-265 C2 10.80 29.12 25.52 54.64 34.57 SiCL -18.9 0.35 270-275 C2 7.31 30.04 33.66 63.70 28.99 SiCL -18.3 0.31 280-285 C2 9.70 28.81 25.80 54.61 36.69 SiCL -18.9 0.35 290-295 C2 6.99 34.43 25.24 59.67 33.34 SiCL -18.3 0.34 300-305 C2 9.52 34.69 24.09 58.78 31.70 SiCL -18.5 0.32 310-315 C2 9.00 33.22 25.28 58.50 32.50 SiCL -19.4 0.36 320-325 C2 14.22 28.00 25.88 53.88 31.90 SiCL -18.7 0.31 330-335 C2 17.31 27.30 23.53 50.83 31.86 SiCL -18.7 0.33 340-345 C2 26.79 22.90 20.89 43.79 29.42 SiCL -19.1 0.29 350-355 C2 14.66 25.18 25.95 51.13 34.21 SiCL -18.5 0.33 360-365 C2 11.58 30.49 27.21 57.70 30.72 SiCL -18.8 0.33 370-375 C2 10.72 31.32 27.21 58.53 30.76 SiCL -19.2 0.27 380-385 C2 5.24 38.20 25.05 63.25 31.51 SiCL -19.2 0.23 390-395 C2 13.33 32.28 21.46 53.74 32.94 SiCL -20.7 0.22 400-405 Cg1 8.47 32.79 25.40 58.19 33.34 SiCL -19.2 0.22 410-415 Cg1 8.50 32.49 23.72 56.21 35.29 SiCL -18.7 0.21 420-425 Cg1 8.03 33.05 23.78 56.83 35.15 SiCL -19.6 0.32 430-435 Cg1 8.33 28.51 25.72 54.23 37.44 SiCL -20.2 0.36 440-445 Cg1 3.94 29.88 28.36 58.24 37.82 SiCL -18.1 0.32 450-455 Cg1 12.74 34.25 20.03 54.28 32.99 SiCL -18.1 0.28 460-465 Cg2 20.38 23.60 24.20 47.80 31.82 CL -18.3 0.37 470-475 Cg2 5.26 34.17 29.29 63.46 31.28 SiCL -18.7 0.96 480-485 Cg2 3.69 37.54 27.23 64.77 31.54 SiCL -21.0 1.58 490-495 Cg2 5.24 37.10 24.90 62.00 32.76 SiCL -19.0 1.18 500-505 Cg2 12.25 26.99 29.68 56.67 31.08 SiCL -20.6 1.12 510-515 Cg2 5.35 35.97 27.03 63.00 31.65 SiCL -22.0 1.69 540-545 Cg2 4.77 36.76 26.48 63.24 31.98 SiCL -19.8 0.74 550-555 Cg2 4.53 36.74 26.35 63.09 32.37 SiCL -19.7 0.92 560-565 Cg2 6.66 28.55 28.47 57.02 36.32 SiCL -20.9 0.73 570-575 2C 7.64 31.66 27.36 59.02 33.34 SiCL -20.5 0.86 580-585 2C 31.18 15.35 23.13 38.48 30.35 CL -20.9 0.35 590-595 2C 8.66 28.80 26.72 55.52 35.82 SiCL -20.0 0.56 600-605 2C 34.67 15.10 22.05 37.15 28.19 CL -20.7 0.34
44 Table 9. Description of Core 1. ______Landform: T-0a Sediment: Alluvium Slope: 1% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Honey Creek Member 0-20 Ap Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary.
20-30 A Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary.
30-49 Bw Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; friable; common fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
49-70 Bk1 Brown (10YR 4/3) heavy silt loam, dark brown (10YR 3/3) moist; weak fine prismatic structure parting to weak fine subangular blocky; friable; common fine threads of calcium carbonate; common fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
70-115 Bk2 Brown (10YR 5/3) silt loam, brown (10YR 4/3) moist; weak medium prismatic structure parting to weak fine prismatic; friable; common threads of calcium carbonate; common fine roots; few worm casts and open worm burrows; common fine and very fine pores; abrupt boundary.
115-150 Akb Dark grayish brown (10YR 4/2) to brown (10YR 4/3) silt loam, very dark grayish brown (10YR 3/2) to dark brown (10YR 3/3) moist; weak fine prismatic structure parting to weak fine subangular blocky; friable; common threads of calcium carbonate; few fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
150-230 Bwb Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; friable; few fine roots; few worm casts and open worm burrows; many very fine and common fine pores; gradual boundary.
230-300 BCb Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; very weak fine subangular blocky structure; friable; few fine roots; few worm casts and open worm burrows; many very fine and common fine pores; gradual boundary.
300-330 Cb Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; massive; friable; interbedded with very dark gray (10YR 3/1) silty clay loam, black (10YR 2/1) moist; few fine roots; many very fine and common fine pores; abrupt boundary.
330-387 Cgb Dark gray (5Y 4/1) clay loam, very dark gray (5Y 3/1) moist; common fine distinct yellowish red (5YR 4/6) mottles; massive; firm; stratified; interbedded with fine gravel; common fine and medium and few coarse pores; abrupt boundary.
387-450 2Cb Stratified chert-rich gravel. ______
45 Table 10. Description of Core 11. ______Landform: T-0a Sediment: Alluvium Slope: 1% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Honey Creek Member 0-20 Ap Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary.
20-45 A Very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; gradual boundary.
45-73 Bw Dark grayish brown (10YR 4/2) to brown (10YR 4/3) silt loam, very dark grayish brown (10YR 3/2) to dark brown (10YR 3/3) moist; weak fine subangular blocky structure; friable; common fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
73-125 Bk1 Brown (10YR 4/3) heavy silt loam, dark brown (10YR 3/3) moist; weak fine prismatic structure parting to weak fine subangular blocky; friable; common fine threads of calcium carbonate; common fine roots; common worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
125-160 Bk2 Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak medium prismatic structure parting to weak fine prismatic; friable; common threads of calcium carbonate; common fine roots; few worm casts and open worm burrows; common fine and very fine pores; abrupt boundary.
160-193 Akb Dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine prismatic structure parting to weak fine subangular blocky; friable; many films and threads of calcium carbonate; common fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary.
193-255 Bwb Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; friable; few fine roots; few worm casts and open worm burrows; many very fine and common fine pores; gradual boundary.
255-277 BCb Brown (10YR 4/3) loam, dark brown (10YR 3/3) moist; very weak fine subangular blocky structure; friable; few fine roots; few worm casts and open worm burrows; many very fine and common fine pores; gradual boundary.
277-285 Cb Olive brown (2.5Y 4/3) gravelly clay loam, dark olive brown (2.5Y 3/3) moist; massive; friable; many pebbles and granules; few fine roots; common fine and very fine pores; abrupt boundary.
285-335 2Cb Stratified chert-rich gravel.
______
46 Table 11. Description of Core 5. ______Landform: T-0a Sediment: Alluvium Slope: 1% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Roberts Creek Member 0-20 Ap Very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; clear boundary. 20-60 A1 Very dark gray (10YR 3/1) silt loam to light silty clay loam, black (10YR 2/1) moist; weak fine granular structure; friable; many fine and very fine roots; many worm casts and open worm burrows; common fine pores; gradual boundary. 60-90 A2 Very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; friable; common fine and very fine roots; many worm casts and open worm burrows; common fine pores; gradual boundary. 90-100 AB Very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure parting to weak fine granular; friable; common fine and very fine roots; common worm casts and open worm burrows; common fine pores; gradual boundary. 100-150 Bw Brown (10YR 4/3) silt loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; friable; few fine and very fine roots; common worm casts and open worm burrows; common fine and very fine pores; clear boundary. 150-180 Ab1 Very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; friable; few fine and very fine roots; common worm casts and open worm burrows; common fine pores; gradual boundary. 180-195 ACb1 Very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; few faint beds of very dark gray (10YR 3/1) silt loam, black (10YR 2/1) moist; very weak fine granular structure; friable; few fine and very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 195-237 Cb1 Laminated very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist and very dark gray (10YR 3/1) silt loam, black (10YR 2/1) moist; few fine faint brown (7.5YR 4/3) mottles; massive; soft, very friable; few very fine roots; common fine and very fine pores; abrupt boundary. 237-262 Ab2 Very dark gray (10YR 3/1) silt loam to light silty clay loam, black (10YR 2/1) moist; weak fine granular structure; friable; few very fine roots; few worm casts and open worm burrows; common fine and very fine pores; gradual boundary. 262-310 ACb2 Very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; very weak fine granular structure; friable; faint bedding; common fine and very fine pores; gradual boundary. 310-340 C1b2 Dark gray (10YR 4/1) silt loam, very dark gray (10YR 3/1) moist; common fine and medium faint dark grayish brown (2.5Y 4/3) and few fine prominent strong brown (7.5YR 4/6) and yellowish red (5YR 4/6) mottles; massive; friable; few small bivalves; few granules and coarse sand grains; few fine pores; gradual boundary. 340-360 C2b2 Dark grayish brown (2.5Y 4/2) gritty clay loam, very dark grayish brown (2.5Y 3/2) moist; few fine prominent strong brown (7.5YR 4/6) and yellowish red (5YR 4/6) mottles; massive; firm; many small bivalves; many granules and coarse sand grains; few fine pores. ______
47 Table 12. Description of Core 7. ______Landform: Alluvial/Colluvial Fan Sediment: Alluvium and colluvium Slope: 2-3% Drainage: Well drained Remarks: Decalcified soil carbon from the upper 10 cm of the Atb horizon yielded a radiocarbon age of 24,560+350 yr B.P. ______Depth Soil (cm) Horizon Description ______Severance Formation 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; common worm casts and open worm burrows; clear boundary.
20-38 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; common worm casts and open worm burrows; gradual boundary.
38-52 BA Dark grayish brown (10YR 4/2) heavy silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; hard; few fine angular pebbles; common fine and very fine roots; common worm casts and open worm burrows; gradual boundary.
52-77 Bt1 Dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate medium angular blocky structure; very hard; common distinct discontinuous clay films on ped faces; few fine angular pebbles; common fine and very fine roots; common worm casts and open worm burrows; few fine pores; gradual boundary.
77-105 Bt2 Brown (10YR 4/3) silty clay, dark brown (10YR 3/3) moist; moderate medium angular blocky structure; very hard; common distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine angular pebbles; few fine and very fine roots; few fine pores; gradual boundary.
105-124 Bt3 Dark yellowish brown (10YR 4/4) silty clay, dark yellowish brown (10YR 3/4) moist; moderate medium angular blocky structure; very hard; common distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine angular pebbles; few fine and very fine roots; common fine and medium pores; gradual boundary.
124-147 Bt4 Brown (7.5YR 5/4) silty clay, brown (7.5YR 4/4) moist; common fine distinct yellowish red (5YR 4/6) mottles; moderate medium angular blocky structure; very hard; common distinct discontinuous brown (7.5YR 5/3) clay films on ped faces; few fine angular pebbles; common fine and medium pores; clear boundary.
147-165 Atb Brown (7.5YR 4/3) silty clay, dark brown (7.5YR 3/3) moist; few fine distinct yellowish red (5YR 4/6) mottles; moderate medium angular blocky structure; very hard; common prominent thick continuous dark brown (7.5YR 3/2) clay films on ped faces and clay flows in macro-pores; few fine angular pebbles; common fine and medium and few coarse pores; gradual boundary.
165-190 Btb Reddish brown (5YR 4/3) silty clay, dark reddish brown (5YR 3/3) moist; common fine distinct yellowish red (5YR 4/6) mottles; moderate medium prismatic structure parting to moderate fine angular blocky; common prominent thick continuous dark brown (7.5YR 3/2) clay films on ped faces and clay flows in macro-pores; few fine hard and soft manganese oxide concretions; few fine angular pebbles; common fine and medium and few coarse pores; gradual boundary.
190-200+ 2Cb Gravelly brown (7.5YR 4/4) silty clay, dark brown (7.5YR 3/4) moist; massive; very hard; angular chert and limestone clasts compose 75% of material by volume. ______
48 Table 13. Description of Core 8. ______Landform: Alluvial/Colluvial Fan Sediment: Alluvium and colluvium Slope: 2-3% Drainage: Well drained Remarks: Decalcified soil carbon from the upper 10 cm of the Atb horizon yielded a radiocarbon age of 22,620+340 yr B.P. ______Depth Soil (cm) Horizon Description ______Severance Formation 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; common worm casts and open worm burrows; clear boundary. 20-30 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; common worm casts and open worm burrows; gradual boundary. 30-40 BA Dark grayish brown (10YR 4/2) heavy silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; hard; few fine angular pebbles; common fine and very fine roots; common worm casts and open worm burrows; gradual boundary. 40-65 Bt1 Dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate medium angular blocky structure; very hard; common distinct discontinuous clay films on ped faces; few fine angular pebbles; common fine and very fine roots; common worm casts and open worm burrows; few fine pores; gradual boundary. 65-80 Bt2 Brown (10YR 4/3) silty clay, dark brown (10YR 3/3) moist; moderate medium angular blocky structure; very hard; common distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine angular pebbles; few fine and very fine roots; few fine pores; gradual boundary. 80-100 Bt3 Dark yellowish brown (10YR 4/4) silty clay, dark yellowish brown (10YR 3/4) moist; moderate medium angular blocky structure; very hard; common distinct discontinuous dark grayish brown (10YR 4/2) clay films on ped faces; few fine angular pebbles; few fine and very fine roots; common fine and medium pores; gradual boundary. 100-124 Bt4 Brown (7.5YR 5/4) silty clay, brown (7.5YR 4/4) moist; common fine distinct yellowish red (5YR 4/6) mottles; moderate medium angular blocky structure; very hard; common distinct discontinuous brown (7.5YR 5/3) clay films on ped faces; few fine angular pebbles; common fine and medium pores; clear boundary. 124-163 Atb Brown (7.5YR 4/3) silty clay, dark brown (7.5YR 3/3) moist; few fine distinct yellowish red (5YR 4/6) mottles; moderate medium angular blocky structure; very hard; common prominent thick continuous dark brown (7.5YR 3/2) clay films on ped faces and clay flows in macro-pores; few fine angular pebbles; common fine and medium and few coarse pores; gradual boundary. 163-203 Bt1b Reddish brown (5YR 4/3) silty clay, dark reddish brown (5YR 3/3) moist; common fine distinct yellowish red (5YR 4/6) mottles; moderate medium prismatic structure parting to moderate fine angular blocky; common prominent thick continuous dark brown (7.5YR 3/2) clay films on ped faces and clay flows in macro-pores; few fine hard and soft manganese oxide concretions; few fine angular pebbles; common fine and medium and few coarse pores; gradual boundary. 203-260 Bt2b Reddish brown (5YR 4/4) heavy silty clay, dark reddish brown (5YR 3/4) moist; common fine distinct yellowish red (5YR 4/6) mottles; strong medium prismatic structure; common distinct discontinuous reddish brown (5YR 4/3) clay films on ped faces and clay flows in macro-pores; many fine manganese oxide coatings on ped faces and common fine hard manganese concretions; few fine angular pebbles; common fine and medium and few coarse pores; gradual boundary. 260-280 BCtb Yellowish brown (10YR 5/8) and reddish yellow (7.5YR 6/8) silty clay, dark yellowish brown (10YR 4/6) and strong brown (7.5YR 5/8) moist; weak medium prismatic structure parting to very weak angular blocky; very hard; common thick distinct brown (7.5YR 4/3) clay flows of ped faces and in macro-pores; many fine manganese oxide coatings on ped faces and common fine hard manganese concretions; common angular pebbles; common fine and medium and few coarse pores; gradual boundary. 280-290+ 2Cb Gravelly brown (7.5YR 4/4) silty clay, dark brown (7.5YR 3/4) moist; massive; very hard; angular chert and limestone clasts compose 75% of material by volume. ______
49 Table 14. Description of Core 10. ______Landform: Alluvial/Colluvial Fan Sediment: Alluvium and colluvium Slope: 2-3% Drainage: Well drained ______Depth Soil (cm) Horizon Description ______Severance Formation 0-20 Ap Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; common worm casts and open worm burrows; clear boundary.
20-35 A Dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; friable; many fine and very fine roots; common worm casts and open worm burrows; gradual boundary.
35-50 BA Dark grayish brown (10YR 4/2) heavy silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; hard; few fine angular pebbles; common fine and very fine roots; common worm casts and open worm burrows; gradual boundary.
50-90 Bt1 Brown (10YR 4/3) heavy silty clay loam, dark brown (10YR 3/3) moist; moderate medium angular blocky structure; very hard; common distinct discontinuous clay films on ped faces; few fine angular pebbles; common fine and very fine roots; common worm casts and open worm burrows; few fine pores; gradual boundary.
90-126 Bt2 Brown (7.5YR 5/4) silty clay, brown (7.5YR 4/4) moist; common fine distinct yellowish red (5YR 4/6) mottles; moderate medium angular blocky structure; very hard; common distinct discontinuous brown (7.5YR 5/3) clay films on ped faces; few fine angular pebbles; common fine and medium pores; clear boundary.
126-135 Atb Brown (7.5YR 4/3) silty clay, dark brown (7.5YR 3/3) moist; few fine distinct yellowish red (5YR 4/6) mottles; moderate medium angular blocky structure; very hard; common prominent thick continuous dark brown (7.5YR 3/2) clay films on ped faces and clay flows in macro-pores; few fine angular pebbles; common fine and medium and few coarse pores; gradual boundary.
135-146 Btb Reddish brown (5YR 4/3) silty clay, dark reddish brown (5YR 3/3) moist; common fine distinct yellowish red (5YR 4/6) mottles; moderate medium prismatic structure parting to moderate fine angular blocky; common prominent thick continuous dark brown (7.5YR 3/2) clay films on ped faces and clay flows in macro-pores; few fine hard and soft manganese oxide concretions; few fine angular pebbles; common fine and medium and few coarse pores; gradual boundary.
146-150 2Cb Gravelly reddish brown (5YR 4/3) silty clay, dark reddish brown (5YR 3/3) moist; massive; very hard; angular chert and limestone clasts compose 80-85% of material by volume.
______
50 Table 15. Organic carbon content and δ13C values for Core 11. Soil Organic Depth Horizon δ13C Carbon (cm) (‰) (%) 0- 5 Ap -23.0 2.47 10- 15 Ap -19.2 1.42 20- 25 A -16.9 1.33 30- 35 A -15.6 1.42 40- 45 A -14.7 1.41 50- 55 Bw -15.1 1.21 60- 65 Bw -15.5 1.06 70- 75 Bw -15.3 0.89 80- 85 Bk1 -15.2 0.78 90- 95 Bk1 -15.0 0.76 100-105 Bk1 -14.9 0.69 110-115 Bk1 -15.0 0.72 120-125 Bk1 -14.7 0.86 130-135 Bk2 -15.3 0.86 140-145 Bk2 -16.4 0.79 150-155 Bk2 -16.4 0.89 160-165 Akb -17.4 1.16 170-175 Akb -16.4 1.08 180-185 Akb -15.8 0.95 190-195 Akb -16.3 1.01 200-205 Bwb -16.0 0.90 210-215 Bwb -15.9 0.96 220-225 Bwb -15.9 0.79 230-235 Bwb -18.0 0.98 240-245 Bwb -16.6 0.75 250-255 Bwb -16.7 0.79 270-275 Cb -16.4 0.67 280-285 Cb -17.4 0.63
Table 16. Preservation potential for buried cultural deposits in Fox Creek valley. ______Cultural Landform Periods T-0a T-0b T-1 Alluvial/Colluvial Fans ______Historic - +++ - - Late Ceramic +++ - - - Middle Ceramic +++ - + - Early Ceramic +++ - +++ - Late Archaic + - +++ - Middle Archaic - - + - Early Archaic - - - - Paleoindian - - ++ ? Pre-Clovis - - - + ______- No potential; + low potential, ++ moderate potential, +++ high potential
51 52